feat: implement deleteSourceObjects for compose operation

- Added deleteSourceObjects to Storage.ComposeRequest and Builder.
- Updated StorageImpl, GrpcStorageImpl, and HttpStorageRpc to support the flag.
- Added unit tests in StorageImplMockitoTest.
- Added integration test in ITObjectTest.
- Addressed PR feedback by directly setting the field in transport implementations.

Co-authored-by: nidhiii-27 <224584462+nidhiii-27@users.noreply.github.com>

Author: google-labs-jules[bot]

java-storage/google-cloud-storage/src/main/java/com/google/cloud/storage/GrpcStorageImpl.java

@@ -645,9 +645,7 @@ public Blob compose(ComposeRequest composeRequest) {
         .forEach(builder::addSourceObjects);
     final Object target = codecs.blobInfo().encode(composeRequest.getTarget());
     builder.setDestination(target);
-    if (composeRequest.isDeleteSourceObjects()) {
-      builder.setDeleteSourceObjects(true);
-    }
+    builder.setDeleteSourceObjects(composeRequest.isDeleteSourceObjects());
     ComposeObjectRequest req = opts.composeObjectsRequest().apply(builder).build();
     GrpcCallContext merge = Utils.merge(grpcCallContext, Retrying.newCallContext());
     return retrier.run(

java-storage/google-cloud-storage/src/main/java/com/google/cloud/storage/spi/v1/HttpStorageRpc.java

@@ -817,9 +817,7 @@ public StorageObject compose(
       sourceObjects.add(sourceObject);
     }
     request.setSourceObjects(sourceObjects);
-    if (Option.DELETE_SOURCE_OBJECTS.getBoolean(targetOptions) != null) {
-      request.setDeleteSourceObjects(Option.DELETE_SOURCE_OBJECTS.getBoolean(targetOptions));
-    }
+    request.setDeleteSourceObjects(Option.DELETE_SOURCE_OBJECTS.getBoolean(targetOptions));
     Span span = startSpan(HttpStorageRpcSpans.SPAN_NAME_COMPOSE);
     Scope scope = tracer.withSpan(span);
     try {