pgsql: Refactor replication origin state reset helpers.

Refactor replication origin state reset helpers.

Factor out common logic for clearing replorigin_session_* variables
into a dedicated helper function, replorigin_xact_clear().

This removes duplicated assignments of these variables across multiple
call sites, and makes the intended scope of each reset explicit.

Author: Chao Li <lic@highgo.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Reviewed-by: Álvaro Herrera <alvherre@kurilemu.de>
Discussion: https://postgr.es/m/CAEoWx2=pYvfRthXHTzSrOsf5_FfyY4zJyK4zV2v4W=yjUij1cA@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/227eb4eea20575d9ef0aac0bdae7b6c2ba261f34

Modified Files
--------------
src/backend/replication/logical/origin.c    | 21 ++++++++++++++++-----
src/backend/replication/logical/tablesync.c |  4 +---
src/backend/replication/logical/worker.c    | 14 ++++++--------
src/include/replication/origin.h            |  3 +++
4 files changed, 26 insertions(+), 16 deletions(-)