pgsql: Add CHECK_FOR_INTERRUPTS in contrib/pg_buffercache functions.

Add CHECK_FOR_INTERRUPTS in contrib/pg_buffercache functions.

This commit adds CHECK_FOR_INTERRUPTS to loops iterating over shared
buffers in several pg_buffercache functions, allowing them to be
interrupted during long-running operations.

Backpatch to all supported versions. Add CHECK_FOR_INTERRUPTS to the
loop in pg_buffercache_pages() in all supported branches, and to
pg_buffercache_summary() and pg_buffercache_usage_counts() in version
16 and newer.

Author: SATYANARAYANA NARLAPURAM <satyanarlapuram(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAHg+QDcejeLx7WunFT3DX6XKh1KshvGKa8F5au8xVhqVvvQPRw@mail.gmail.com
Backpatch-through: 13

Branch
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REL_17_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/b6090ed96b60374560251c6f3ec65309c9ce4b96

Modified Files
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contrib/pg_buffercache/pg_buffercache_pages.c | 6 ++++++
1 file changed, 6 insertions(+)