pgsql: Update FSM in COPY FREEZE replay

Update FSM in COPY FREEZE replay

d96f87332b3 folded COPY FREEZE visibility map updates into
XLOG_HEAP2_MULTI_INSERT records. Unlike the former XLOG_HEAP2_VISIBLE
redo path, multi-insert redo only updated the FSM when the record did
not contain a heap page FPI and the heap page had less than 20% free
space.

This can leave all-frozen pages with missing or stale FSM entries on a
standby. After promotion, vacuum will skip those pages, preventing
their free space from being discovered.

When a multi-insert record sets the page all-frozen, record the heap
page's free space unconditionally.

Reported-by: Melanie Plageman <melanieplageman(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAAKRu_bS3nfMJCF2fjE%2Bceb5-t%3D2p_VPMk2PWuVomrOFxg5DGQ%40mail.gmail.com
Backpatch-through: 19

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/f7700080dc4c9226dd0fd81795214c02635e474d

Modified Files
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src/backend/access/heap/heapam_xlog.c | 46 ++++++++++++++++++++++++-----------
1 file changed, 32 insertions(+), 14 deletions(-)