Review fixes for jdbc:javaagent (#18061)

Co-authored-by: otelbot <197425009+otelbot@users.noreply.github.com>

Author: otelbot[bot]

instrumentation/jdbc/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/jdbc/DriverInstrumentation.java

@@ -19,6 +19,7 @@
 import io.opentelemetry.javaagent.extension.instrumentation.TypeTransformer;
 import java.sql.Connection;
 import java.util.Properties;
+import javax.annotation.Nullable;
 import net.bytebuddy.asm.Advice;
 import net.bytebuddy.description.type.TypeDescription;
 import net.bytebuddy.matcher.ElementMatcher;
@@ -52,7 +53,7 @@ public static class DriverAdvice {
     public static void addDbInfo(
         @Advice.Argument(0) String url,
         @Advice.Argument(1) Properties props,
-        @Advice.Return Connection connection) {
+        @Advice.Return @Nullable Connection connection) {
       if (connection == null) {
         // Exception was probably thrown.
         return;

instrumentation/jdbc/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/jdbc/datasource/DataSourceInstrumentation.java

@@ -44,10 +44,10 @@ public static class GetConnectionAdvice {
 
     public static class AdviceScope {
       private final CallDepth callDepth;
-      private final Context context;
-      private final Scope scope;
+      @Nullable private final Context context;
+      @Nullable private final Scope scope;
 
-      private AdviceScope(CallDepth callDepth, Context context, Scope scope) {
+      private AdviceScope(CallDepth callDepth, @Nullable Context context, @Nullable Scope scope) {
         this.callDepth = callDepth;
         this.context = context;
         this.scope = scope;
@@ -75,7 +75,8 @@ public static AdviceScope start(DataSource ds) {
         return new AdviceScope(callDepth, context, context.makeCurrent());
       }
 
-      public void end(@Nullable Throwable throwable, DataSource ds, Connection connection) {
+      public void end(
+          @Nullable Throwable throwable, DataSource ds, @Nullable Connection connection) {
         if (callDepth.decrementAndGet() > 0) {
           return;
         }