pgsql: aio: Add errcontext for processing I/Os for another backend

aio: Add errcontext for processing I/Os for another backend

Push an ErrorContextCallback adding additional detail about the process
performing the I/O and the owner of the I/O when those are not the same.

For io_method worker, this adds context specifying which process owns
the I/O that the I/O worker is processing.

For io_method io_uring, this adds context only when a backend is
*completing* I/O for another backend. It specifies the pid of the owning
process.

Author: Melanie Plageman <melanieplageman(at)gmail(dot)com>
Reviewed-by: Andres Freund <andres(at)anarazel(dot)de>
Discussion: https://postgr.es/m/rdml3fpukrqnas7qc5uimtl2fyytrnu6ymc2vjf2zuflbsjuul%40hyizyjsexwmm

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b3219c69fc1e161df8d380c464b3f2cce3b6cab9

Modified Files
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src/backend/storage/aio/method_io_uring.c | 31 +++++++++++++++++++++++++++++++
src/backend/storage/aio/method_worker.c | 29 +++++++++++++++++++++++++++++
2 files changed, 60 insertions(+)