approval-voting: Make sure we always mark approved candidates approved in a...

approval-voting: Make sure we always mark approved candidates approved in a different relay chain context (#4153)

... see for more detail why this is needed

https://github.com/paritytech/polkadot-sdk/issues/4149#issuecomment-2058472444

## TODO:
- [x] Unittests
- [x] Replicate scenario from
https://github.com/paritytech/polkadot-sdk/issues/4149 and confirm this
fixes it: https://github.com/paritytech/polkadot-sdk/issues/4149 [
Replicated on a zombienet with some hacked nodes, that we can end up in
this state where no-wake is schedule and the nodes are pending new
assignments]

---------

Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com>