aio: Use runtime arguments with injections points in tests

aio: Use runtime arguments with injections points in tests

This cleans up the code related to the testing infrastructure of AIO
that used injection points, switching the test code to use the new
facility for injection points added by 371f2db8b05e rather than tweaks
to pass and reset arguments to the callbacks run.

This removes all the dependencies to USE_INJECTION_POINTS in the AIO
code.  pgaio_io_call_inj(), pgaio_inj_io_get() and pgaio_inj_cur_handle
are now gone.

Reviewed-by: Greg Burd <greg@burd.me>
Discussion: https://postgr.es/m/Z_y9TtnXubvYAApS@paquier.xyz