Simplify Operations by uniting Sync and Async operations into a single interface.

Merged Async Read / Write Operations into their sync operations counterparts.

* AsyncWriteOperation into WriteOperation is a simple merge
* AsyncReadOperation into ReadOperation requires an additional type parameter
  This is due to async and sync cursors have different types.

Added extra ReadOperations interfaces to represent:
  * Read operations that return the same type for sync / async
  * Read operations that represent cursors

Removed SyncOperations and AsyncOperations builders which both use the same Operations builder class.

JAVA-4900

Author: rozza

driver-core/src/main/com/mongodb/internal/operation/AbstractWriteSearchIndexOperation.java

@@ -37,7 +37,7 @@
  *
  * <p>This class is not part of the public API and may be removed or changed at any time</p>
  */
-abstract class AbstractWriteSearchIndexOperation implements AsyncWriteOperation<Void>, WriteOperation<Void> {
+abstract class AbstractWriteSearchIndexOperation implements WriteOperation<Void> {
     private final MongoNamespace namespace;
 
     AbstractWriteSearchIndexOperation(final MongoNamespace namespace) {

driver-core/src/main/com/mongodb/internal/operation/AggregateOperation.java

@@ -41,7 +41,7 @@
  *
  * <p>This class is not part of the public API and may be removed or changed at any time</p>
  */
-public class AggregateOperation<T> implements AsyncExplainableReadOperation<AsyncBatchCursor<T>>, ExplainableReadOperation<BatchCursor<T>> {
+public class AggregateOperation<T> implements ReadOperationExplainable<T> {
     private final AggregateOperationImpl<T> wrapped;
 
     public AggregateOperation(final MongoNamespace namespace, final List<BsonDocument> pipeline, final Decoder<T> decoder) {
@@ -151,13 +151,7 @@ public void executeAsync(final AsyncReadBinding binding, final SingleResultCallb
     }
 
     @Override
-    public <R> ReadOperation<R> asExplainableOperation(@Nullable final ExplainVerbosity verbosity, final Decoder<R> resultDecoder) {
-        return createExplainableOperation(verbosity, resultDecoder);
-    }
-
-    @Override
-    public <R> AsyncReadOperation<R> asAsyncExplainableOperation(@Nullable final ExplainVerbosity verbosity,
-                                                                 final Decoder<R> resultDecoder) {
+    public <R> ReadOperationSimple<R> asExplainableOperation(@Nullable final ExplainVerbosity verbosity, final Decoder<R> resultDecoder) {
         return createExplainableOperation(verbosity, resultDecoder);
     }
 

driver-core/src/main/com/mongodb/internal/operation/AggregateOperationImpl.java

@@ -52,7 +52,7 @@
 import static com.mongodb.internal.operation.SyncOperationHelper.CommandReadTransformer;
 import static com.mongodb.internal.operation.SyncOperationHelper.executeRetryableRead;
 
-class AggregateOperationImpl<T> implements AsyncReadOperation<AsyncBatchCursor<T>>, ReadOperation<BatchCursor<T>> {
+class AggregateOperationImpl<T> implements ReadOperationCursor<T> {
     private static final String COMMAND_NAME = "aggregate";
     private static final String RESULT = "result";
     private static final String CURSOR = "cursor";

driver-core/src/main/com/mongodb/internal/operation/AggregateToCollectionOperation.java

@@ -54,7 +54,7 @@
  *
  * <p>This class is not part of the public API and may be removed or changed at any time</p>
  */
-public class AggregateToCollectionOperation implements ReadOperation<Void>, AsyncReadOperation<Void> {
+public class AggregateToCollectionOperation implements ReadOperationSimple<Void> {
     private static final String COMMAND_NAME = "aggregate";
     private final MongoNamespace namespace;
     private final List<BsonDocument> pipeline;