udpate and rebase to QEMU v6.0.0

udpate and rebase to QEMU v6.0.0

Mostly minor changes, bigger ones summarized:
* QEMU's internal backup code now uses a new async system, which allows
  parallel requests - the default max_workers settings is 64, I chose
  less, since 64 put enough stress on QEMU that the guest became
  practically unusable during the backup, and 16 still shows quite a
  nice measureable performance improvement. Little code changes for us
  though.
* 'malformed' QAPI parameters/functions are now a build error (i.e.
  using '_' vs '-'), I chose to just whitelist our calls in the name of
  backwards compatibility.
* monitor OOB race fix now uses the upstream variant, cherry-picked from
  origin/master since it's not in 6.0 by default
* last patch fixes a bug with snapshot rollback related to the new yank
  system

Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>