[HUDI-2469] [Kafka Connect] Replace json based payload with protobuf for Transaction protocol. (#3694)

* Substitue Control Event with protobuf

* Fix tests

* Fix unit tests

* Add javadocs

* Add javadocs

* Address reviewer comments

Co-authored-by: Rajesh Mahindra <rmahindra@Rajeshs-MacBook-Pro.local>

hudi-kafka-connect/src/main/resources/log4j.properties

@@ -0,0 +1,23 @@
+###
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+###
+log4j.rootLogger=INFO, A1
+# A1 is set to be a ConsoleAppender.
+log4j.appender.A1=org.apache.log4j.ConsoleAppender
+# A1 uses PatternLayout.
+log4j.appender.A1.layout=org.apache.log4j.PatternLayout
+log4j.appender.A1.layout.ConversionPattern=%-4r [%t] %-5p %c %x - %m%n