pgsql: Convert heap_vac_scan_next_block() boolean parameters to flags

Convert heap_vac_scan_next_block() boolean parameters to flags

The read stream API only allows one piece of extra per block state to be
passed back to the API user (per_buffer_data). lazy_scan_heap() needs
two pieces of per-buffer data: whether or not the block was all-visible
in the visibility map and whether or not it was eagerly scanned.

Convert these two pieces of information to flags so that they can be
populated by heap_vac_scan_next_block() and returned to
lazy_scan_heap(). A future commit will turn heap_vac_scan_next_block()
into the read stream callback for heap phase I vacuuming.

Reviewed-by: Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
Reviewed-by: Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAAKRu_bmx33jTqATP5GKNFYwAg02a9dDtk4U_ciEjgBHZSVkOQ%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/32acad7d1d0a83a1815e15fe28b421d3471ef774

Modified Files
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src/backend/access/heap/vacuumlazy.c | 47 +++++++++++++++++++++---------------
1 file changed, 27 insertions(+), 20 deletions(-)