vmdk: mark more functions as coroutine_fns and GRAPH_RDLOCK

Mark functions as coroutine_fn when they are only called by other coroutine_fns
and they can suspend.  Change calls to co_wrappers to use the non-wrapped
functions, which in turn requires adding GRAPH_RDLOCK annotations.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20230601115145.196465-9-pbonzini@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>