[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-spark-bundle/pom.xml

@@ -60,6 +60,9 @@
                   <resource>META-INF/LICENSE</resource>
                   <file>target/classes/META-INF/LICENSE</file>
                 </transformer>
+                <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
+                  <resource>META-INF/services/org.apache.spark.sql.sources.DataSourceRegister</resource>
+                </transformer>
               </transformers>
               <artifactSet>
                 <includes>
@@ -69,6 +72,7 @@
                   <include>org.apache.hudi:hudi-spark-common_${scala.binary.version}</include>
                   <include>org.apache.hudi:hudi-spark_${scala.binary.version}</include>
                   <include>org.apache.hudi:${hudi.spark.module}_${scala.binary.version}</include>
+                  <include>org.apache.hudi:${hudi.spark.common.module}</include>
                   <include>org.apache.hudi:hudi-hive-sync</include>
                   <include>org.apache.hudi:hudi-sync-common</include>
                   <include>org.apache.hudi:hudi-hadoop-mr</include>
@@ -249,6 +253,11 @@
       <artifactId>${hudi.spark.module}_${scala.binary.version}</artifactId>
       <version>${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.hudi</groupId>
       <artifactId>hudi-timeline-service</artifactId>