io_uring: include all deps for alloc_cache.h

alloc_cache.h uses types it doesn't declare and thus depends on the
order in which it's included. Make it self contained and pull all needed
definitions.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Gabriel Krisman Bertazi <krisman@suse.de>
Link: https://lore.kernel.org/r/39569f3d5b250b4fe78bb609d57f67d3736ebcc4.1738087204.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>