[SPARK-3660][STREAMING] Initial RDD for updateStateByKey transformation

SPARK-3660 : Initial RDD for updateStateByKey transformation

I have added a sample StatefulNetworkWordCountWithInitial inspired by StatefulNetworkWordCount.

Please let me know if any changes are required.

Author: Soumitra Kumar <kumar.soumitra@gmail.com>

Closes #2665 from soumitrak/master and squashes the following commits:

ee8980b [Soumitra Kumar] Fixed copy/paste issue.
304f636 [Soumitra Kumar] Added simpler version of updateStateByKey API with initialRDD and test.
9781135 [Soumitra Kumar] Fixed test, and renamed variable.
3da51a2 [Soumitra Kumar] Adding updateStateByKey with initialRDD API to JavaPairDStream.
2f78f7e [Soumitra Kumar] Merge remote-tracking branch 'upstream/master'
d4fdd18 [Soumitra Kumar] Renamed variable and moved method.
d0ce2cd [Soumitra Kumar] Merge remote-tracking branch 'upstream/master'
31399a4 [Soumitra Kumar] Merge remote-tracking branch 'upstream/master'
4efa58b [Soumitra Kumar] [SPARK-3660][STREAMING] Initial RDD for updateStateByKey transformation
8f40ca0 [Soumitra Kumar] Merge remote-tracking branch 'upstream/master'
dde4271 [Soumitra Kumar] Merge remote-tracking branch 'upstream/master'
fdd7db3 [Soumitra Kumar] Adding support of initial value for state update. SPARK-3660 : Initial RDD for updateStateByKey transformation