pgsql: aio: Add pg_aios view

aio: Add pg_aios view

The new view lists all IO handles that are currently in use and is mainly
useful for PG developers, but may also be useful when tuning PG.

Bumps catversion.

Reviewed-by: Noah Misch <noah@leadboat.com>
Discussion: https://postgr.es/m/uvrtrknj4kdytuboidbhwclo4gxhswwcpgadptsjvjqcluzmah%40brqs62irg4dt

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/60f566b4f24362f54003569d5f6e24137bcd83fc

Modified Files
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doc/src/sgml/system-views.sgml           | 294 +++++++++++++++++++++++++++++++
src/backend/catalog/system_views.sql     |   7 +
src/backend/storage/aio/Makefile         |   1 +
src/backend/storage/aio/aio_funcs.c      | 230 ++++++++++++++++++++++++
src/backend/storage/aio/meson.build      |   1 +
src/include/catalog/catversion.h         |   2 +-
src/include/catalog/pg_proc.dat          |   9 +
src/test/regress/expected/privileges.out |  18 ++
src/test/regress/expected/rules.out      |  16 ++
src/test/regress/sql/privileges.sql      |   3 +
10 files changed, 580 insertions(+), 1 deletion(-)