[SPARK-56923][SDP] Implement SCD1 Batch Processor; Merge Microbatch onto Auxiliary

[AnishMahto]

Approved AutoCDC SPIP: https://lists.apache.org/thread/j6sj9wo9odgdpgzlxtvhoy7szs0jplf7

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This is a stacked PR. Review incremental diff here: AnishMahto/spark@SPARK-56249-merge-tombstones-onto-microbatch...SPARK-56923-SCD1-merge-microbatch-onto-auxiliary

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Preamble:

The SCD type 1 flow is a foreachBatch streaming query on an input change-data-feed, and is responsible for reconciling the incoming change data onto some target table that follows SCD1 replication semantics.

SCD1 flows also maintain an "auxiliary" table to keep track of early-arriving out-of-order received events state. Each microbatch will need to reconcile against this auxiliary table as well, and update the auxiliary table's state appropriately for future microbatches.

Merge Microbatch onto Auxiliary:

The auxiliary table should be updated such that;

1. Stale tombstones (delete events now succeeded by upserts/deletes in the incoming microbatch) should be removed from the auxiliary table. They will never be meaningful for SCD1 again.
2. New tombstones introduced in the incoming microbatch should be persisted in the auxiliary table, for future microbatches to reconcile agianst.

Implement this update operation as a MERGE.