Track replica origin progress for Rollback Prepared

While reviewing logical decoding of 2PC xacts work, I noticed that we
need $SUBJECT [1]. Commit 1eb6d6527a [2] allowed to track replica
origin replay progress for 2PC but it was not complete. It misses to
properly track the progress for rollback prepared especially it missed
to update the code for recovery. Additionally, we need to allow
tracking it on subscriber nodes where
wal_level might not be logical.

As noted in [1], without this the subscriber might again ask for
rollback prepared lsn after restart.

Attached patch addresses this problem.

Thoughts?

[1] - https://www.postgresql.org/message-id/CAA4eK1L3p4z%2B9wtK77MbdpkagR4GS2Y3r1Je7ZEvLQVF9GArfg%40mail.gmail.com
[2] -
commit 1eb6d6527aae264b3e0b9c95aa70bb7a594ad1cf
Author: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Date: Wed Mar 28 17:42:50 2018 +0100

Store 2PC GID in commit/abort WAL recs for logical decoding

Store GID of 2PC in commit/abort WAL records when wal_level = logical.
This allows logical decoding to send the SAME gid to subscribers
across restarts of logical replication.

Track relica origin replay progress for 2PC.

--
With Regards,
Amit Kapila.