[HUDI-1296] Support Metadata Table in Spark Datasource (#4789)

* Bootstrapping initial support for Metadata Table in Spark Datasource

- Consolidated Avro/Row conversion utilities to center around Spark's AvroDeserializer ; removed duplication
- Bootstrapped HoodieBaseRelation
- Updated HoodieMergeOnReadRDD to be able to handle Metadata Table
- Modified MOR relations to be able to read different Base File formats (Parquet, HFile)

pom.xml

@@ -349,6 +349,7 @@
           <configuration>
             <rerunFailingTestsCount>3</rerunFailingTestsCount>
             <argLine>@{argLine}</argLine>
+            <trimStackTrace>false</trimStackTrace>
             <systemPropertyVariables>
               <log4j.configuration>
                 ${surefire-log4j.file}