pgsql: aio: Rename pgaio_io_prep_* to pgaio_io_start_*

aio: Rename pgaio_io_prep_* to pgaio_io_start_*

The old naming pattern (mirroring liburing's naming) was inconsistent with
the (not yet introduced) callers. It seems better to get rid of the
inconsistency now than to grow more users of the odd naming.

Reported-by: Noah Misch <noah(at)leadboat(dot)com>
Discussion: https://postgr.es/m/20250326001915.bc.nmisch@google.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/9469d7fdd2bcf2327ad91a1022885953a461942a

Modified Files
--------------
src/backend/storage/aio/aio.c | 16 ++++++++--------
src/backend/storage/aio/aio_callback.c | 2 +-
src/backend/storage/aio/aio_io.c | 24 ++++++++++++------------
src/backend/storage/aio/aio_target.c | 4 ++--
src/include/storage/aio.h | 6 +++---
src/include/storage/aio_internal.h | 4 ++--
6 files changed, 28 insertions(+), 28 deletions(-)