Bridges - backport changes/nits as a part of preparation for Bridges V2

[bkontur]

Contains migration of changes/nits/refactors from https://github.com/paritytech/polkadot-sdk/pull/4427 which are not directly affecting bridges pallets for Bridges V2 (dynamic lanes).

TODO

• [ ] rebase on actual master, at least this should work:

cargo test -p bp-header-chain -p bp-messages -p bp-parachains -p bp-polkadot-core -p bp-relayers -p bp-runtime -p bp-test-utils -p bp-xcm-bridge-hub -p bp-xcm-bridge-hub-router -p bp-beefy  -p bp-westend -p bp-rococo -p bp-polkadot-bulletin -p bp-polkadot -p bp-kusama -p bp-bridge-hub-westend -p bp-bridge-hub-rococo -p bp-bridge-hub-cumulus -p bp-bridge-hub-kusama -p bp-bridge-hub-polkadot  -p bridge-runtime-common  -p relay-substrate-client -p substrate-relay-helper -p finality-relay -p messages-relay -p parachains-relay -p relay-utils -p equivocation-detector  -p pallet-bridge-beefy -p pallet-bridge-grandpa -p pallet-bridge-messages -p pallet-bridge-parachains -p pallet-bridge-relayers -p pallet-xcm-bridge-hub -p pallet-xcm-bridge-hub-router  --features runtime-benchmarks,try-runtime,integrity-test

• [ ] cherry-pick other commits

[svyatonik]

@svyatonik In traitified v2 client we are using shared subscriptions, so https://github.com/paritytech/polkadot-sdk/pull/4481 shouldn't be a problem when we talk about long-lived subscriptions (justification). But we need to test it for transaction subscriptions - right now I've rebased completely without #4481