pgsql: Avoid setting pd_prune_xid when inserting frozen tuples

Avoid setting pd_prune_xid when inserting frozen tuples

378a216187a set pd_prune_xid on inserts so that on-access pruning could
later set the pages all-visible. heap_multi_insert() skipped this only
when setting the page all-frozen, but it can insert frozen tuples even
when not setting the page all-frozen. Inserting frozen tuples should not
set pd_prune_xid as they introduce no work for on-access pruning. Fix by
only setting pd_prune_xid when inserting non-frozen tuples.

Reported-by: Melanie Plageman <melanieplageman(at)gmail(dot)com>
Reviewed-by: Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAAKRu_a02pu7U2S0qPZ5L%2BoWb2m2Zp965sOKCCLnKUAKNo-hfg%40mail.gmail.com
Backpatch-through: 19

Branch
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REL_19_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/41a8548ad41854d88578aebcfdf54bbdca42d49e

Modified Files
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src/backend/access/heap/heapam.c | 6 +++---
src/backend/access/heap/heapam_xlog.c | 21 ++++++++++++++++-----
2 files changed, 19 insertions(+), 8 deletions(-)