fix: fix scaladoc warnings across all modules

Motivation:
The project had scaladoc warnings about unresolvable links,
ambiguous overloads, and incorrect package prefixes across actor,
actor-typed, stream, cluster, serialization-jackson, persistence,
and other modules.

Modification:
- Replace unresolvable [[...]] links with backtick-quoted code for external types
- Fix incorrect package prefixes (pekko. -> org.apache.pekko.)
- Resolve ambiguous overload links using backtick-quoted code
- Fix @throws tags with fully qualified type names
- Fix variable references in code blocks (Helpers.scala)

Result:
All scaladoc warnings are resolved across the affected modules.

Tests:
Verified with `sbt doc` on affected subprojects - 0 warnings.

References:
None - scaladoc cleanup

Author: He-Pin

actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/Effect.scala

@@ -49,8 +49,8 @@ object Effect {
    * The 'replyToRef' is exposed so that the target inbox can expect the actual message sent to
    * initiate the ask.
    *
-   * Note that this requires the ask to be initiated via the [[ActorContext]].  The [[Future]] returning
-   * ask is not testable in the [[BehaviorTestKit]].
+   * Note that this requires the ask to be initiated via the [[ActorContext]].  The `Future` returning
+   * ask is not testable in the `BehaviorTestKit`.
    */
   final case class AskInitiated[Req, Res, T](target: RecipientRef[Req],
       responseTimeout: FiniteDuration,

actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/javadsl/BehaviorTestKit.scala

@@ -86,7 +86,7 @@ abstract class BehaviorTestKit[T] {
   def runAsk[Res](messageFactory: JFunction[ActorRef[Res], T]): ReplyInbox[Res]
 
   /**
-   * The same as [[runAsk]], but with the response class specified.  This improves type inference in Java
+   * The same as `runAsk`, but with the response class specified.  This improves type inference in Java
    * when asserting on the reply in the same statement as the `runAsk` as in:
    *
    * ```
@@ -102,14 +102,14 @@ abstract class BehaviorTestKit[T] {
     runAsk(messageFactory)
 
   /**
-   * The same as [[runAsk]] but only for requests that result in a response of type [[pekko.pattern.StatusReply]].
+   * The same as `runAsk` but only for requests that result in a response of type [[pekko.pattern.StatusReply]].
    *
    * @since 1.3.0
    */
   def runAskWithStatus[Res](messageFactory: JFunction[ActorRef[StatusReply[Res]], T]): StatusReplyInbox[Res]
 
   /**
-   * The same as [[runAskWithStatus]], but with the response class specified.  This improves type inference in
+   * The same as `runAskWithStatus`, but with the response class specified.  This improves type inference in
    * Java when asserting on the reply in the same statement as the `runAskWithStatus` as in:
    *
    * ```

actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/javadsl/TestKitJUnit5Extension.scala

@@ -28,7 +28,7 @@ final class TestKitJUnit5Extension() extends AfterAllCallback with BeforeTestExe
   var testKit: Option[ActorTestKit] = None
 
   /**
-   * Get a reference to the field annotated with `@JUnit5Testkit` [[JUnit5TestKit]]
+   * Get a reference to the field annotated with `@JUnit5TestKit`
    */
   override def beforeTestExecution(context: ExtensionContext): Unit = {
     val testInstance: Option[AnyRef] =

actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/javadsl/TestKitJUnitJupiterExtension.scala

@@ -27,7 +27,7 @@ final class TestKitJUnitJupiterExtension() extends AfterAllCallback with BeforeT
   var testKit: Option[ActorTestKit] = None
 
   /**
-   * Get a reference to the field annotated with `@JUnitJupiterTestKit` [[JUnitJupiterTestKit]]
+   * Get a reference to the field annotated with `@JUnitJupiterTestKit` `JUnitJupiterTestKit`
    */
   override def beforeTestExecution(context: ExtensionContext): Unit = {
     val testInstance: Option[AnyRef] =

actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/javadsl/TestProbe.scala

@@ -69,8 +69,8 @@ object TestProbe {
 }
 
 /**
- * Java API: * Create instances through the `create` factories in the [[TestProbe]] companion
- * or via [[ActorTestKit#createTestProbe]].
+ * Java API: Create instances through the `create` factories in the `TestProbe` companion
+ * or via `ActorTestKit.createTestProbe`.
  *
  * A test probe is essentially a queryable mailbox which can be used in place of an actor and the received
  * messages can then be asserted etc.

actor-typed/src/main/scala/org/apache/pekko/actor/typed/ActorSystem.scala

@@ -34,7 +34,7 @@ import com.typesafe.config.{ Config, ConfigFactory }
 
 /**
  * An ActorSystem is home to a hierarchy of Actors. It is created using
- * [[ActorSystem#apply]] from a [[Behavior]] object that describes the root
+ * `ActorSystem.apply` from a [[Behavior]] object that describes the root
  * Actor of this hierarchy and which will create all other Actors beneath it.
  * A system also implements the [[ActorRef]] type, and sending a message to
  * the system directs that message to the root Actor.

actor-typed/src/main/scala/org/apache/pekko/actor/typed/SupervisorStrategy.scala

@@ -36,7 +36,7 @@ object SupervisorStrategy {
 
   /**
    * Restart immediately without any limit on number of restart retries. A limit can be
-   * added with [[RestartSupervisorStrategy.withLimit]].
+   * added with `RestartSupervisorStrategy.withLimit`.
    *
    * If the actor behavior is deferred and throws an exception on startup the actor is stopped
    * (restarting would be dangerous as it could lead to an infinite restart-loop)
@@ -358,7 +358,7 @@ sealed abstract class BackoffSupervisorStrategy extends SupervisorStrategy {
    * The initial errors are logged at the level defined with [[BackoffSupervisorStrategy.withLogLevel]].
    * For example, the first 3 errors can be logged at INFO level and thereafter at ERROR level.
    *
-   * The counter (and log level) is reset after the [[BackoffSupervisorStrategy.withResetBackoffAfter]]
+   * The counter (and log level) is reset after the `BackoffSupervisorStrategy.withResetBackoffAfter`
    * duration.
    */
   def withCriticalLogLevel(criticalLevel: Level, afterErrors: Int): BackoffSupervisorStrategy

actor-typed/src/main/scala/org/apache/pekko/actor/typed/javadsl/AskPattern.scala

@@ -55,7 +55,7 @@ object AskPattern {
   /**
    * The same as [[ask]] but only for requests that result in a response of type [[pekko.pattern.StatusReply]].
    * If the response is a [[pekko.pattern.StatusReply#success]] the returned future is completed successfully with the wrapped response.
-   * If the status response is a [[pekko.pattern.StatusReply#error]] the returned future will be failed with the
+   * If the status response is a `StatusReply.error` the returned future will be failed with the
    * exception in the error (normally a [[pekko.pattern.StatusReply.ErrorMessage]]).
    */
   def askWithStatus[Req, Res](

actor/src/main/scala/org/apache/pekko/actor/ActorSelection.scala

@@ -95,7 +95,7 @@ abstract class ActorSelection extends Serializable {
   def resolveOne(timeout: FiniteDuration): Future[ActorRef] = resolveOne()(timeout)
 
   /**
-   * Java API for [[#resolveOne]]
+   * Java API for `resolveOne`
    *
    * Resolve the [[ActorRef]] matching this selection.
    * The result is returned as a CompletionStage that is completed with the [[ActorRef]]
@@ -337,7 +337,7 @@ private[pekko] case object SelectParent extends SelectionPathElement {
 }
 
 /**
- * When [[ActorSelection#resolveOne]] can't identify the actor the
+ * When `ActorSelection.resolveOne` can't identify the actor the
  * `Future` is completed with this failure.
  */
 @SerialVersionUID(1L)

actor/src/main/scala/org/apache/pekko/actor/FSM.scala

@@ -693,7 +693,7 @@ trait FSM[S, D] extends Actor with Listeners with ActorLogging {
    *
    * An initial `currentState -> currentState` notification will be triggered by calling this method.
    *
-   * @see [[#startWith]]
+   * @see `startWith`
    */
   final def initialize(): Unit =
     if (currentState ne null) makeTransition(currentState)