pgsql: Fix tuple search during apply after concurrent index DDL.

Fix tuple search during apply after concurrent index DDL.

When searching the local relation by index, the apply worker can use the
first match only if the index is the relation's replica identity or
primary key. Otherwise, every match must be compared with the search slot.

Only the index OID was saved in the relation map, so this was determined
again during the search. Concurrent DROP INDEX or REINDEX can change the
index status between these two checks, causing the tuple search to fail
and the change to be silently skipped as an update_missing conflict.

Fix this by recording the answer as idxisreplident in the relation map
entry and avoid getting it second time in FindReplTupleInLocalRel() and
RelationFindReplTupleByIndex().

Oversight in 89e46da5e5.

Author: Mikhail Nikalayeu <mihailnikalayeu(at)gmail(dot)com>
Author: vignesh C <vignesh21(at)gmail(dot)com>
Reviewed-by: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Reviewed-by: Zhijie Hou <houzj(dot)fnst(at)fujitsu(dot)com>
Discussion: https://postgr.es/m/CADzfLwUJovFcnknCC9wjZKECX9xecgnGzC2r2TMV8h4QDD_jwQ@mail.gmail.com
Backpatch-through: 16, where it was introduced

Branch
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REL_19_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/2f7bf51b7b0866cfacfd8b483351412d27cdb1e1

Modified Files
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src/backend/executor/execReplication.c | 18 +--
src/backend/replication/logical/conflict.c | 4 +
src/backend/replication/logical/relation.c | 18 ++-
src/backend/replication/logical/worker.c | 94 +++++++++------
src/include/executor/executor.h | 2 +
src/include/replication/logicalrelation.h | 4 +
src/test/subscription/t/032_subscribe_use_index.pl | 127 +++++++++++++++++++++
7 files changed, 217 insertions(+), 50 deletions(-)