pgsql: Convert AIO to use the new shmem allocation functions

Convert AIO to use the new shmem allocation functions

This replaces the "shmem_size" and "shmem_init" callbacks in the IO
methods table with the same ShmemCallback struct that we now use in
other subsystems

Reviewed-by: Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>
Reviewed-by: Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>
Reviewed-by: Daniel Gustafsson <daniel(at)yesql(dot)se>
Discussion: https://www.postgresql.org/message-id/CAExHW5vM1bneLYfg0wGeAa=52UiJ3z4vKd3AJ72X8Fw6k3KKrg@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/58a1573385edb28435913affe626ff7daffba76d

Modified Files
--------------
src/backend/storage/aio/aio_init.c | 112 ++++++++++++++++++------------
src/backend/storage/aio/method_io_uring.c | 38 +++++-----
src/backend/storage/aio/method_worker.c | 84 +++++++++-------------
src/backend/storage/ipc/ipci.c | 2 -
src/include/storage/aio_internal.h | 16 +----
src/include/storage/aio_subsys.h | 3 -
src/include/storage/subsystemlist.h | 3 +
7 files changed, 127 insertions(+), 131 deletions(-)