Adjust existing pairs of non-coroutine and coroutine functions to share
the same calling convention, and add non-coroutine/coroutine
counterparts where they don't exist.
Also make the non-coroutine versions generated_co_wrappers.
This series sits on top of "[PATCH v5 00/10] Implement
bdrv_{pread,pwrite,pwrite_sync,pwrite_zeroes}() using
generated_co_wrapper":
https://lore.kernel.org/qemu-devel/20220609152744.3891847-1-afaria@redhat.com/
Based-on: <20220609152744.3891847-1-afaria@redhat.com>
v2:
- Avoid using variables named 'len' or similar to hold return values
from blk_{pread,pwrite}(), as they don't return a length anymore.
- Drop variables in_ret and out_ret in qemu-img.c:img_dd().
- Initialize buf in test_sync_op_blk_pwritev_part().
- Keep blk_co_copy_range() in the "I/O API functions" section of
include/sysemu/block-backend-io.h.