Open channel input should not require IP and port

Currently, when we want to open a channel we require the whole URI for a node, but the IP and port is not necessary.

For example, if Core Lightning only gets the pubkey of a node, it'll try all known addresses instead of only the one which is given via the API.

Start at the API endpoint that handles opening a channel and trace how the node URI is validated or passed to Core Lightning. Confirm the expected behavior for a pubkey-only request and verify that Core Lightning can try all known addresses when no IP or port is supplied.

Written by the indexing model from the issue text.