blockdev: refactor transaction to use Transaction API

We are going to add more block-graph modifying transaction actions,
and block-graph modifying functions are already based on Transaction
API.

Next, we'll need to separately update permissions after several
graph-modifying actions, and this would be simple with help of
Transaction API.

So, now let's just transform what we have into new-style transaction
actions.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-Id: <20230510150624.310640-2-vsementsov@yandex-team.ru>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>