streamrestore: workaround for notification volume
stream_restore_subscribe has not been implemented on pipewire yet. Since streamrestore relies on the call back to update the volume slider and mute button status, users are unable to interact with those. This workaround uses the cached values instead.
Revert when fix is released for https://gitlab.freedesktop.org/pipewire/pipewire/-/issues/3805
BUG: 473013 (cherry picked from commit 881d852f3d6bc9a608897e85f103bdcca9080abe)