pgsql: WAL log VM setting for empty pages in XLOG_HEAP2_PRUNE_VACUUM_SC

WAL log VM setting for empty pages in XLOG_HEAP2_PRUNE_VACUUM_SCAN

As part of removing XLOG_HEAP2_VISIBLE records, phase I of VACUUM now
marks empty pages all-visible and all-frozen in a
XLOG_HEAP2_PRUNE_VACUUM_SCAN record.

This has no real independent benefit, but empty pages were the last user
of XLOG_HEAP2_VISIBLE, so by making this change we can next remove all
of the XLOG_HEAP2_VISIBLE code.

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
Earlier version Reviewed-by: Robert Haas <robertmhaas@gmail.com>

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/a759ced2f1e2f817005c1b8ee92d0626764da7d1

Modified Files
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src/backend/access/heap/pruneheap.c  | 33 ++++++++++++++++++---------
src/backend/access/heap/vacuumlazy.c | 44 ++++++++++++++++++++++--------------
2 files changed, 49 insertions(+), 28 deletions(-)