Remove `pallet::getter` usage from bridges/modules (#7120)

# Description

Part of #3326 

As per title, the `pallet:getter` usage has been removed from:
- `pallet-bridge-beefy`
- `pallet-bridge-grandpa`
- `pallet-bridge-messages`
- `pallet-bridge-relayers`
- `pallet-xcm-bridge-hub-router`


polkadot address: 12poSUQPtcF1HUPQGY3zZu2P8emuW9YnsPduA4XG3oCEfJVp

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Co-authored-by: Branislav Kontur <bkontur@gmail.com>
Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>