[backport] Snowbridge free consensus updates (#5201) (#5560)

Allow free Snowbridge consensus updates, if the header interval is
larger than the configured value (set to 32, so once a epoch).

This PR also moves the Rococo Snowbridge pallet config into its own
module.

Original PR: https://github.com/Snowfork/polkadot-sdk/pull/159

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Original `pr_5201.prdoc` is present but moved to release dir, ergo
`R0-Silent` for this backport PR.

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Co-authored-by: Clara van Staden <[email protected]>
Co-authored-by: Francisco Aguirre <[email protected]>