pgsql: aio: Basic subsystem initialization

aio: Basic subsystem initialization

This commit just does the minimal wiring up of the AIO subsystem, added in the
next commit, to the rest of the system. The next commit contains more details
about motivation and architecture.

This commit is kept separate to make it easier to review, separating the
changes across the tree, from the implementation of the new subsystem.

We discussed squashing this commit with the main commit before merging AIO,
but there has been a mild preference for keeping it separate.

Reviewed-by: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
Reviewed-by: Noah Misch <noah(at)leadboat(dot)com>
Discussion: https://postgr.es/m/uvrtrknj4kdytuboidbhwclo4gxhswwcpgadptsjvjqcluzmah%40brqs62irg4dt

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/02844012b304ba80d1c48d51f6fe10bb622490cc

Modified Files
--------------
doc/src/sgml/config.sgml | 51 +++++++++++++++
src/backend/access/transam/xact.c | 12 ++++
src/backend/postmaster/autovacuum.c | 2 +
src/backend/postmaster/bgwriter.c | 2 +
src/backend/postmaster/checkpointer.c | 2 +
src/backend/postmaster/pgarch.c | 2 +
src/backend/postmaster/walsummarizer.c | 2 +
src/backend/postmaster/walwriter.c | 2 +
src/backend/replication/walsender.c | 2 +
src/backend/storage/aio/Makefile | 2 +
src/backend/storage/aio/aio.c | 90 +++++++++++++++++++++++++++
src/backend/storage/aio/aio_init.c | 37 +++++++++++
src/backend/storage/aio/meson.build | 2 +
src/backend/storage/ipc/ipci.c | 3 +
src/backend/utils/init/postinit.c | 7 +++
src/backend/utils/misc/guc_tables.c | 23 +++++++
src/backend/utils/misc/postgresql.conf.sample | 6 ++
src/backend/utils/resowner/resowner.c | 29 +++++++++
src/include/storage/aio.h | 38 +++++++++++
src/include/storage/aio_subsys.h | 33 ++++++++++
src/include/utils/guc.h | 1 +
src/include/utils/guc_hooks.h | 2 +
src/include/utils/resowner.h | 5 ++
src/tools/pgindent/typedefs.list | 1 +
24 files changed, 356 insertions(+)