Summary:
Transactional DDL introduces support for interleaving DDL and DML statements within a transaction block.

A few tests are yet to be fixed to work with txn ddl. Txn ddl has been disabled in such tests with GH issues for tracking them:

1. TestDropTableWithConcurrentTxn: #29141
2. TestPgCacheConsistency: #29142
3. TestPgRegressIndex: #29143
Jira: DB-1839

Test Plan: Jenkins

Reviewers: pjain, myang, bkolagani, patnaik.balivada, rthallam

Reviewed By: rthallam

Subscribers: rthallam, skumar, yql

Differential Revision: https://phorge.dev.yugabyte.com/D47922