block: drop wrapper for bdrv_set_backing_hd_drained()

block: drop wrapper for bdrv_set_backing_hd_drained()

Nearly all callers (outside of the tests) are already using the
_drained() variant of the function. It doesn't seem worth keeping.
Simply adapt the remaining callers of bdrv_set_backing_hd() and rename
bdrv_set_backing_hd_drained() to bdrv_set_backing_hd().

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-ID: <20250530151125.955508-31-f.ebner@proxmox.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>