[HUDI-3172] Refactor hudi existing modules to make more code reuse in V2 Implementation (#4514)

* Introduce hudi-spark3-common and hudi-spark2-common modules to place classes that would be reused in different spark versions, also introduce hudi-spark3.1.x to support spark 3.1.x.
* Introduce hudi format under hudi-spark2, hudi-spark3, hudi-spark3.1.x modules and change the hudi format in original hudi-spark module to hudi_v1 format.
* Manually tested on Spark 3.1.2 and Spark 3.2.0 SQL.
* Added a README.md file under hudi-spark-datasource module.

packaging/hudi-integ-test-bundle/pom.xml

@@ -74,6 +74,7 @@
                   <include>org.apache.hudi:hudi-utilities_${scala.binary.version}</include>
                   <include>org.apache.hudi:hudi-spark_${scala.binary.version}</include>
                   <include>org.apache.hudi:${hudi.spark.module}_${scala.binary.version}</include>
+                  <include>org.apache.hudi:${hudi.spark.common.module}</include>
                   <include>org.apache.hudi:hudi-hive-sync</include>
                   <include>org.apache.hudi:hudi-sync-common</include>
                   <include>org.apache.hudi:hudi-hadoop-mr</include>
@@ -350,6 +351,12 @@
       <version>${project.version}</version>
     </dependency>
 
+    <dependency>
+      <groupId>org.apache.hudi</groupId>
+      <artifactId>${hudi.spark.common.module}</artifactId>
+      <version>${project.version}</version>
+    </dependency>
+
     <dependency>
       <groupId>org.apache.hadoop</groupId>
       <artifactId>hadoop-hdfs</artifactId>