iotests: add filter_qmp_generated_node_ids()

iotests: add filter_qmp_generated_node_ids()

Add a filter function for QMP responses that contain QEMU's
automatically generated node ids. The ids change between runs and must
be masked in the reference output.

The next commit will use this new function.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20240118144823.1497953-2-stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit da62b507a20510d819bcfbe8f5e573409b954006)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
(Mjt: context fix in tests/qemu-iotests/iotests.py due to
 v7.2.0-939-gbcc6777ad6 "iotests: Filter child node information")