Bridge: added force_set_pallet_state call to pallet-bridge-grandpa (#4465)

closes https://github.com/paritytech/parity-bridges-common/issues/2963

See issue above for rationale
I've been thinking about adding similar calls to other pallets, but:
- for parachains pallet I haven't been able to think of a case when we
will need that given how long referendum takes. I.e. if storage proof
format changes and we want to unstuck the bridge, it'll take a large a
few weeks to sync a single parachain header, then another weeks for
another and etc.
- for messages pallet I've made the similar call initially, but it just
changes a storage key (`OutboundLanes` and/or `InboundLanes`), so
there's no any logic here and it may be simply done using
`system.set_storage`.

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Co-authored-by: command-bot <>