pgsql: Separate TBM[Shared|Private]Iterator and TBMIterateResult

Separate TBM[Shared|Private]Iterator and TBMIterateResult

Remove the TBMIterateResult member from the TBMPrivateIterator and
TBMSharedIterator and make tbm_[shared|private_]iterate() take a
TBMIterateResult as a parameter.

This allows tidbitmap API users to manage multiple TBMIterateResults per
scan. This is required for bitmap heap scan to use the read stream API,
with which there may be multiple I/Os in flight at once, each one with a
TBMIterateResult.

Reviewed-by: Tomas Vondra <tomas(at)vondra(dot)me>
Discussion: https://postgr.es/m/d4bb26c9-fe07-439e-ac53-c0e244387e01%40vondra.me

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/944e81bf99db2b5b70b8a389d4f273534da73f74

Modified Files
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src/backend/access/gin/ginget.c | 33 ++++++-----
src/backend/access/gin/ginscan.c | 2 +-
src/backend/access/heap/heapam_handler.c | 28 +++++----
src/backend/executor/nodeBitmapHeapscan.c | 39 ++++++-------
src/backend/nodes/tidbitmap.c | 96 +++++++++++++++++--------------
src/include/access/gin_private.h | 7 ++-
src/include/nodes/tidbitmap.h | 6 +-
7 files changed, 110 insertions(+), 101 deletions(-)