Tracking issue: kvdb/postgres-Remove global application level lock

[saubyk]

Need to remove the global application level lock from the postgres backend. This lock prevents multiple write transactions from happening at the same time, and will also block a writer if a read is on going.

There was a pr merged to address the issue: #8644. The change since has been reverted with this pr: #9212

Would need a new pr to address the global application level lock issue