pgsql: Add maintenance_io_concurrency flag to some read stream users

Add maintenance_io_concurrency flag to some read stream users

Index vacuuming and [auto]prewarm AIO concurrency should be governed by
maintenance_io_concurrency. As such, pass those read stream users the
READ_STREAM_MAINTENANCE flag which will calculate their read stream
distance with maintenance_io_concurrency instead of
effective_io_concurrency. This was an oversight in the original commits
making those operations use the read stream API.

Discussion: https://postgr.es/m/flat/CAAKRu_aopDxTo4b41Mt_7Zc-z0_ngocrY8SFCCY6Aph1HgwuNw%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/f132815fd717f26613dcc3888608044eac91a7ac

Modified Files
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contrib/pg_prewarm/autoprewarm.c | 3 ++-
contrib/pg_prewarm/pg_prewarm.c | 3 ++-
src/backend/access/gist/gistvacuum.c | 3 ++-
src/backend/access/nbtree/nbtree.c | 3 ++-
src/backend/access/spgist/spgvacuum.c | 3 ++-
5 files changed, 10 insertions(+), 5 deletions(-)