Collator Protocol Revamp: send PeerId via UMP

[alindima]

This is the parachain side of the revamp, which needs to add a new optional type of inherent data, containing the peerid of the current node. It should be optional, so that existing collators ignore this new field and new collators populate it.

The parachain-system pallet needs to process this new inherent if present and send the corresponding UMP signal, but only if the runtime is explicitly configured to do so. This should only happen after the relay chain validators are updated to be able to decode the new message and the node feature is enabled.

The node side could always send the new inherent data, as it should be ignored by the runtime before an upgrade.