update submodule and patches to 7.2.0

User-facing breaking change:

The slirp submodule for user networking got removed. It would be
necessary to add the --enable-slirp option to the build and/or install
the appropriate library to continue building it. Since PVE is not
explicitly supporting it, it would require additionally installing the
libslirp0 package on all installations and there is *very* little
mention on the community forum when searching for "slirp" or
"netdev user", the plan is to only enable it again if there is some
real demand for it.

Notable changes:

* The big change for this release is the rework of job locking, using
  a job mutex and introducing _locked() variants of job API functions
  moving away from call-side AioContext locking. See (in the qemu
  submodule) commit 6f592e5aca ("job.c: enable job lock/unlock and
  remove Aiocontext locks") and previous commits for context.

  Changes required for the backup patches:
  * Use WITH_JOB_LOCK_GUARD() and call the _locked() variant of job
    API functions where appropriate (many are only availalbe as
    a _locked() variant).
  * Remove acquiring/releasing AioContext around functions taking the
    job mutex lock internally.

  The patch introducing sequential transaction support for jobs needs
  to temporarily unlock the job mutex to call job_start() when
  starting the next job in the transaction.

* The zeroinit block driver now marks its child as primary.

  The documentation in include/block/block-common.h states:
  > Filter node has exactly one FILTERED|PRIMARY child, and may have
  > other children which must not have these bits

  Without this, an assert will trigger when copying to a zeroinit target
  with qemu-img convert, because bdrv_child_cb_attach() expects any
  non-PRIMARY child to be not FILTERED:
  > qemu-img convert -n -p -f raw -O raw input.raw zeroinit:output.raw
  > qemu-img: ../block.c:1476: bdrv_child_cb_attach: Assertion
  > `!(child->role & BDRV_CHILD_FILTERED)' failed.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>

debian/patches/pve/0013-PVE-virtio-balloon-improve-query-balloon.patch

@@ -58,10 +58,10 @@ index 73ac5eb675..bbfe7eca62 100644
  
  static void virtio_balloon_to_target(void *opaque, ram_addr_t target)
 diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
-index c6cd6f91dd..15572befb1 100644
+index 01b789a79e..480b798963 100644
 --- a/monitor/hmp-cmds.c
 +++ b/monitor/hmp-cmds.c
-@@ -715,7 +715,35 @@ void hmp_info_balloon(Monitor *mon, const QDict *qdict)
+@@ -696,7 +696,35 @@ void hmp_info_balloon(Monitor *mon, const QDict *qdict)
          return;
      }
  
@@ -99,7 +99,7 @@ index c6cd6f91dd..15572befb1 100644
      qapi_free_BalloonInfo(info);
  }
 diff --git a/qapi/machine.json b/qapi/machine.json
-index 6afd1936b0..8b4be9b718 100644
+index b9228a5e46..10e77a9af3 100644
 --- a/qapi/machine.json
 +++ b/qapi/machine.json
 @@ -1054,9 +1054,29 @@