Mark MultiChildLoadBalancer as Internal. (#10481)

* Mark MultiChildLoadBalancer as Internal.  Cannot move to the internal package because of its use of classes in the util package.

* Exclude MultiChildLoadBalancer from javadoc generation.

* Fix javadoc creation.

all/build.gradle

@@ -22,6 +22,7 @@ def subprojects = [
     project(':grpc-servlet-jakarta'),
     project(':grpc-stub'),
     project(':grpc-testing'),
+    project(':grpc-util'),
     project(':grpc-xds'),
 ]
 

gae-interop-testing/gae-jdk8/build.gradle

@@ -166,3 +166,7 @@ tasks.register("runInteropTestRemote") {
         throw new GradleException("Interop test failed:\nthrowable:${caught}")
     }
 }
+
+tasks.named("javadoc").configure {
+    enabled = false
+}

util/build.gradle

@@ -37,3 +37,7 @@ animalsniffer {
         sourceSets.test
     ]
 }
+
+tasks.named("javadoc").configure {
+    exclude 'io/grpc/util/MultiChildLoadBalancer.java'
+}

util/src/main/java/io/grpc/util/MultiChildLoadBalancer.java

@@ -24,6 +24,7 @@ import static io.grpc.ConnectivityState.TRANSIENT_FAILURE;
 
 import com.google.common.annotations.VisibleForTesting;
 import io.grpc.ConnectivityState;
+import io.grpc.Internal;
 import io.grpc.LoadBalancer;
 import io.grpc.LoadBalancerProvider;
 import io.grpc.Status;
@@ -40,10 +41,9 @@ import javax.annotation.Nullable;
 
 /**
  * A base load balancing policy for those policies which has multiple children such as
- * ClusterManager or the petiole policies.
+ * ClusterManager or the petiole policies.  For internal use only.
- *
- * @since 1.58
  */
+@Internal
 public abstract class MultiChildLoadBalancer extends LoadBalancer {
 
   @VisibleForTesting