pgsql: Use WAL insert position for conflict detection.

Use WAL insert position for conflict detection.

The retain_dead_tuples feature waits for concurrent transactions to be
applied before advancing conflict_detection_slot.xmin. It gets the WAL
write position from the publisher and waits until the apply remote
position passes it. This ensures that dead tuples, commit timestamps, and
origins needed for conflict detection (update_deleted,
update_origin_differs, and delete_origin_differs) are retained while
those transactions are applied.

However, with asynchronous commit enabled on the publisher, a committed
transaction may not have updated the WAL write position yet. As a result,
the reported WAL position can lag behind the latest committed transaction.
This can cause conflict_detection_slot.xmin to advance prematurely,
allowing dead tuples needed for conflict detection to be removed before
subsequent asynchronously committed transactions are applied.

Report the end of the last inserted WAL record instead. A transaction
inserts its commit record before it is marked committed, so the insert
position cannot be behind a transaction that has already committed.
Transactions that have entered the commit phase but have not yet inserted
their commit record are still accounted for by the in-commit transaction
ID reported in the same message.

In addition to above, add missing trailing period to update_deleted
conflict detail messages which are added for the same feature.

Reported-by: Nisha Moond <nisha(dot)moond412(at)gmail(dot)com>
Author: Zhijie Hou <houzj(dot)fnst(at)fujitsu(dot)com>
Reviewed-by: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Discussion: https://postgr.es/m/TY4PR01MB177182F547A62FC2666EC04EC94B72@TY4PR01MB17718.jpnprd01.prod.outlook.com
Backpatch-through: 19, where it was introduced

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/5f3a49abf7ff7bb4a9eba7101eb8e8021960074f

Modified Files
--------------
src/backend/replication/logical/conflict.c | 8 ++++----
src/backend/replication/logical/worker.c | 6 +++---
src/backend/replication/walsender.c | 25 ++++++++++++++++++++++++-
3 files changed, 31 insertions(+), 8 deletions(-)