pgsql: Drop the temporary tuple slots allocated by pgoutput.

Drop the temporary tuple slots allocated by pgoutput.

In pgoutput, when converting the child table's tuple format to match the
parent table's, we temporarily create a new slot to store the converted
tuple. However, we missed to drop such temporary slots, leading to
resource leakage.

Reported-by: Bowen Shi
Author: Hou Zhijie
Reviewed-by: Amit Kapila
Backpatch-through: 15
Discussion: https://postgr.es/m/CAM_vCudv8dc3sjWiPkXx5F2b27UV7_YRKRbtSCcE-pv=cVACGA@mail.gmail.com

Branch
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REL_16_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/b8f953d8d7bff6ca5d7fc8cb0f37a9d3d7a7462b

Modified Files
--------------
src/backend/replication/pgoutput/pgoutput.c | 10 ++++++++++
1 file changed, 10 insertions(+)