Rename `GetPeerList` and `PeerList` messages

[StephenButtolph]

get_peerlist and peerlist messages often treat peerlist like a single word. Whereas all the other messages get_accepted, pull_query, ect, are named consistently.

We should rename get_peerlist to get_peers.
We should rename peerlist to peers.

This will also impact some CLI flags, as peer-list options should become peers options.

[MukulKolpe]

Hey @StephenButtolph, can I work on this issue?

[StephenButtolph]

@MukulKolpe Absolutely! If you have any questions feel free to ping here

[github-actions]

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