update submodule and patches to QEMU 8.1.2

Bigger notable changes:

* Commit 1a30b0f5d7 ("block: .bdrv_open is non-coroutine and
  unlocked") broke the PVE backup patches, in particular setting up
  the backup dump block driver, because bdrv_new_open_driver() cannot
  be called from a coroutine. To fix it, bdrv_co_open() is used
  instead, and while it's a much more involved function, the result
  should be essentially the same. The only difference I noticed is
  that the BDRV_O_ALLOW_RDWR flag is also set in the resulting bds
  (block driver state), but that shouldn't hurt.

Smaller notable changes:

* aio_set_fd_handler() dropped its 'is_external' parameter stating
  that all callers now pass false in 60f782b6b7 ("aio: remove
  aio_disable_external() API"). The calls in the PVE patches also
  passed false, so just drop the parameter too.

* global_state_store() does not have a return value anymore, so the
  user in the PVE savevm-async patch was adapted. For context, see
  c33f1829f8 ("migration: never fail in global_state_store()").

* Renames affecting the PVE savevm-async patch:
  migrate_use_block() -> migrate_block() and ram_counters -> mig_stats
  9d4b1e5f22 ("migration: Move migrate_use_block() to options.c")
  aff3f6606d ("migration: Rename ram_counters to mig_stats")

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

debian/patches/pve/0037-PVE-block-stream-increase-chunk-size.patch

@@ -11,7 +11,7 @@ Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
  1 file changed, 1 insertion(+), 1 deletion(-)
 
 diff --git a/block/stream.c b/block/stream.c
-index 7f9e1ecdbb..6a29d80398 100644
+index e522bbdec5..afed72db55 100644
 --- a/block/stream.c
 +++ b/block/stream.c
 @@ -27,7 +27,7 @@ enum {