pgsql: Keep all_frozen updated in heap_page_prune_and_freeze

Keep all_frozen updated in heap_page_prune_and_freeze

Previously, we relied on all_visible and all_frozen being used together
to ensure that all_frozen was correct, but it is better to keep both
fields updated.

Future changes will separate their usage, so we should not depend on
all_visible for the validity of all_frozen.

Author: Melanie Plageman <melanieplageman(at)gmail(dot)com>
Reviewed-by: Kirill Reshke <reshkekirill(at)gmail(dot)com>
Discussion: https://postgr.es/m/flat/CAAKRu_ZMw6Npd_qm2KM%2BFwQ3cMOMx1Dh3VMhp8-V7SOLxdK9-g%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/351d7e244183ee33400c19e4b52c5446eb29038c

Modified Files
--------------
src/backend/access/heap/pruneheap.c | 60 ++++++++++++++++++++----------------
src/backend/access/heap/vacuumlazy.c | 9 +++---
2 files changed, 37 insertions(+), 32 deletions(-)