Improve description of some WAL records with transaction commands

Improve description of some WAL records with transaction commands

This commit improves the description of some WAL records for the
Transaction RMGR:
- Track remote_apply for a transaction commit.  This GUC is
user-settable, so this information can be useful for debugging.
- Add replication origin information for PREPARE TRANSACTION, with the
origin ID, LSN and timestamp
- Same as above, for ROLLBACK PREPARED.

This impacts the format of pg_waldump or anything using these
description routines, so no backpatch is done.

Author: Masahiko Sawada, Michael Paquier
Discussion: https://postgr.es/m/CAD21AoD2dJfgsdxk4_KciAZMZQoUiCvmV9sDpp8ZuKLtKCNXaA@mail.gmail.com