Allow adding extra request-response protocols during polkadot service
initialization. This is required to add a request-response protocol
described in
[RFC-0008](https://polkadot-fellows.github.io/RFCs/approved/0008-parachain-bootnodes-dht.html)
to the relay chain side of the parachain node.

### Review notes
The PR might look scary due to a lot of code being moved. It is easier
to review it on a per-commit basis. The commits do not containing
changes to the code logic are named accordingly.

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