chore: bump Gradle from 8.12 to 9.0.0

* Update `Property`/`Provider` usages to require
  `Any` as an upper-bound

Author: EdricChan03

gradle/wrapper/gradle-wrapper.jar

@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.12-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.0.0-bin.zip
 networkTimeout=10000
 validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME

gradle/wrapper/gradle-wrapper.properties

@@ -33,7 +33,7 @@ public abstract class KoogleApiGeneratorPluginExtension {
     public abstract val discoveryDocsOutputDir: DirectoryProperty
 
     /** Mapping function used to generate the output file name based from the specified [DirectoryItem]. */
-    public abstract val outputFileNameMapper: Property<SchemaFileNameMapper?>
+    public abstract val outputFileNameMapper: Property<SchemaFileNameMapper>
 
     /** Mapping function used to generate the output file name based from the specified [DirectoryItem]. */
     public fun outputFileNameMapper(mapper: SchemaFileNameMapper) {

gradlew

@@ -11,16 +11,16 @@ import kotlin.reflect.KMutableProperty0
 /**
  * Sets the receiver property only if the [other] provider [has a value][Provider.isPresent].
  */
-internal fun <T> Property<T>.setIfPresent(other: Provider<out T?>) {
+internal fun <T : Any> Property<T>.setIfPresent(other: Provider<out T>) {
     if (other.isPresent) set(other)
 }
 
 /**
  * Sets the receiver mutable Kotlin property only if the [other] provider
  * [has a value][Provider.isPresent].
  */
-internal fun <T> KMutableProperty0<T>.setIfPresent(other: Provider<out T?>) {
-    if (other.isPresent) other.get()?.let { set(it) }
+internal fun <T : Any> KMutableProperty0<T>.setIfPresent(other: Provider<out T>) {
+    if (other.isPresent) set(other.get())
 }
 
 /**