Unify the operating mode for bridge pallets

- define the OperationMode trait and BasicOperatingMode enum
- use the OperationMode trait in all the bridge pallets
- use BasicOperatingMode instead of IsHalted for the Grandpa pallet
- use BasicOperatingMode as part of MessagesOperatingMode

Signed-off-by: Serban Iorga <[email protected]>

* remove duplicate parachain heads exension

* fix benchmarks compilation

* actually fix it

* added parachains pallet benchmarks

* deduplicate insertion of bridged header

* pruning weight

* fixes

* fix compilation

* added trackerd parachains filter + changed some docs

* fix compilation

* parachains finality

* parachains pallet test

* demo of how to configure GRANDPA pallet instance

* allow instances in parachains pallet

* spellcheck

* TODO + fix

* fmt

* removed invalid storage_keys file

* change all hashers to Blake2_128Concat

* use Twox64Concat for insertion position

* fix build

* fix compilation

* change ParaId and ParaHead types

* TODOs -> TODOs with issues refs