update submodule and patches to 7.1.0

update submodule and patches to 7.1.0

Notable changes:
* The only big change is the switch to using a custom QIOChannel for
  savevm-async, because the previously used QEMUFileOps was dropped.

  Changes to the current implementation:

  * Switch to vector based methods as required for an IO channel. For
    short reads the passed-in IO vector is stuffed with zeroes at the
    end, just to be sure.

  * For reading: The documentation in include/io/channel.h states that
    at least one byte should be read, so also error out when whe are
    at the very end instead of returning 0.

  * For reading: Fix off-by-one error when request goes beyond end.

    The wrong code piece was:
    if ((pos + size) > maxlen) {
        size = maxlen - pos - 1;
    }

    Previously, the last byte would not be read. It's actually
    possible to get a snapshot .raw file that has content all the way
    up the final 512 byte (= BDRV_SECTOR_SIZE) boundary without any
    trailing zero bytes (I wrote a script to do it).

    Luckily, it didn't cause a real issue, because qemu_loadvm_state()
    is not interested in the final (i.e. QEMU_VM_VMDESCRIPTION)
    section. The buffer for reading it is simply freed up afterwards
    and the function will assume that it read the whole section, even
    if that's not the case.

  * For writing: Make use of the generated blk_pwritev() wrapper
    instead of manually wrapping the coroutine to simplify and save a
    few lines.

* Adapt to changed interfaces for blk_{pread,pwrite}:
  * a9262f551e ("block: Change blk_{pread,pwrite}() param order")
  * 3b35d4542c ("block: Add a 'flags' param to blk_pread()")
  * bf5b16fa40 ("block: Make blk_{pread,pwrite}() return 0 on success")
  Those changes especially affected the qemu-img dd patches, because
  the context also changed, but also some of our block drivers used
  the functions.

* Drop qemu-common.h include: it got renamed after essentially
  everything was moved to other headers. The only remaining user I
  could find for things dropped from the header between 7.0 and 7.1
  was qemu_get_vm_name() in the iscsi-initiatorname patch, but it
  already includes the header to which the function was moved.

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