pgsql: Merge prune, freeze and vacuum WAL record formats

Merge prune, freeze and vacuum WAL record formats

The new combined WAL record is now used for pruning, freezing and 2nd
pass of vacuum. This is in preparation for changing VACUUM to write a
combined prune+freeze record per page, instead of separate two
records. The new WAL record format now supports that, but the code
still always writes separate records for pruning and freezing.

This reserves separate XLOG_HEAP2_* info codes for when the pruning
record is emitted for on-access pruning or VACUUM, per Peter
Geoghegan's suggestion. The record format is identical, but having
separate info codes makes it easier analyze pruning and vacuuming with
pg_waldump.

The function to emit the new WAL record, log_heap_prune_and_freeze(),
is in pruneheap.c. The existing heap_log_freeze_plan() and its
subroutines are moved to pruneheap.c without changes, to keep them
together with log_heap_prune_and_freeze().

Author: Melanie Plageman <melanieplageman(at)gmail(dot)com>
Discussion: https://www.postgresql.org/message-id/CAAKRu_azf-zH%3DDgVbquZ3tFWjMY1w5pO8m-TXJaMdri8z3933g@mail.gmail.com
Discussion: https://www.postgresql.org/message-id/CAAKRu_b2oE4GL%3Dq4g9mcByS9yT7wTQvEH9OLpabj28e%2BWKFi2A@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/f83d709760d84253b539ee454ce9ce1ceb9ad9ac

Modified Files
--------------
src/backend/access/gist/gistxlog.c | 8 +-
src/backend/access/hash/hash_xlog.c | 9 +-
src/backend/access/heap/heapam.c | 473 ++++++++-----------------------
src/backend/access/heap/pruneheap.c | 407 ++++++++++++++++++++++----
src/backend/access/heap/vacuumlazy.c | 24 +-
src/backend/access/rmgrdesc/heapdesc.c | 230 ++++++++++-----
src/backend/replication/logical/decode.c | 6 +-
src/include/access/heapam.h | 19 +-
src/include/access/heapam_xlog.h | 220 +++++++++-----
src/include/access/xlog_internal.h | 2 +-
src/tools/pgindent/typedefs.list | 7 +-
11 files changed, 805 insertions(+), 600 deletions(-)