added new proxy ParaRegistration to Westend (#6995)

This adds a new Proxy type to Westend Runtime called ParaRegistration.
This is related to:
https://github.com/polkadot-fellows/runtimes/pull/520.

This new proxy allows:
1. Reserve paraID
2. Register Parachain
3. Leverage Utilites pallet
4. Remove proxy.

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Co-authored-by: command-bot <>
Co-authored-by: Dónal Murray <donal.murray@parity.io>