pgsql: Add a test for commit ac0e33136a using the injection point.

Add a test for commit ac0e33136a using the injection point.

This test uses an injection point to bypass the time overhead caused by
the idle_replication_slot_timeout GUC, which has a minimum value of one
minute.

Author: Hayato Kuroda <kuroda(dot)hayato(at)fujitsu(dot)com>
Author: Nisha Moond <nisha(dot)moond412(at)gmail(dot)com>
Reviewed-by: Peter Smith <smithpb2250(at)gmail(dot)com>
Reviewed-by: Vignesh C <vignesh21(at)gmail(dot)com>
Reviewed-by: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Discussion: https://postgr.es/m/CALj2ACW4aUe-_uFQOjdWCEN-xXoLGhmvRFnL8SNw_TZ5nJe+aw@mail.gmail.com

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/8a695d7998be67445b9cd8e67faa684d4e87a40d

Modified Files
--------------
src/backend/replication/slot.c | 34 +++++--
src/test/recovery/meson.build | 1 +
.../recovery/t/044_invalidate_inactive_slots.pl | 105 +++++++++++++++++++++
3 files changed, 131 insertions(+), 9 deletions(-)