[HUDI-1013] Adding Bulk Insert V2 implementation (#1834)

- Adding ability to use native spark row writing for bulk_insert
 - Controlled by `ENABLE_ROW_WRITER_OPT_KEY` datasource write option
 - Introduced KeyGeneratorInterface in hudi-client, moved KeyGenerator back to hudi-spark
 - Simplified the new API additions to just two new methods : getRecordKey(row), getPartitionPath(row)
 - Fixed all built-in key generators with new APIs
 - Made the field position map lazily created upon the first call to row based apis
 - Implemented native row based key generators for CustomKeyGenerator
 - Fixed all the tests, with these new APIs

Co-authored-by: Balaji Varadarajan <varadarb@uber.com>
Co-authored-by: Vinoth Chandar <vinoth@apache.org>

hudi-common/src/test/resources/timestamp-test-evolved.avsc

@@ -21,6 +21,6 @@
   "name": "User",
   "fields": [
     {"name": "field1", "type": ["null", "string"], "default": null},
-    {"name": "createTime", "type": ["null", "string"], "default": null}
+    {"name": "createTime", "type": ["null", "long"], "default": null}
   ]
 }