Implement RPC endpoint to fetch a baker's alternative consensus key

The update_consensus_key feature introduced in Lima allows a baker to set alternative pubkeys for signing future consensus operations. The currently active and several pending consensus keys are available with the RPC response to https://rpc.ghost.tzstats.com/chains/main/blocks/head/context/delegates/tz1Qf1pSbJzMN4VtGFfVJRgbXhBksRv36TxW and the new https://rpc.ghost.tzstats.com/chains/main/blocks/head/context/delegates/tz1Qf1pSbJzMN4VtGFfVJRgbXhBksRv36TxW/consensus_key. However the response only contains the address (pubkeyhash), but not the pubkey itself. To my knowledge there is no alternative RPC endpoint to fetch this key.

Please add the pubkey to either RPC response (or both) as it is required to validate signatures on blocks and operations signed by this key.