pgsql: Fix EXPLAIN Bitmap heap scan to count pages with no visible tupl

Fix EXPLAIN Bitmap heap scan to count pages with no visible tuples

Previously, bitmap heap scans only counted lossy and exact pages for
explain when there was at least one visible tuple on the page.

heapam_scan_bitmap_next_block() returned true only if there was a
"valid" page with tuples to be processed. However, the lossy and exact
page counters in EXPLAIN should count the number of pages represented
in a lossy or non-lossy way in the constructed bitmap, regardless of
whether or not the pages ultimately contained visible tuples.

Backpatch to all supported versions.

Author: Melanie Plageman
Discussion: https://www.postgresql.org/message-id/CAAKRu_ZwCwWFeL_H3ia26bP2e7HiKLWt0ZmGXPVwPO6uXq0vaA@mail.gmail.com
Discussion: https://www.postgresql.org/message-id/CAAKRu_bxrXeZ2rCnY8LyeC2Ls88KpjWrQ%2BopUrXDRXdcfwFZGA@mail.gmail.com

Branch
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REL_13_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/992189a3e94d27f555c856626c2d45b898571826

Modified Files
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src/backend/executor/nodeBitmapHeapscan.c     | 10 +++++-----
src/test/regress/expected/partition_prune.out |  5 ++++-
2 files changed, 9 insertions(+), 6 deletions(-)