[wireguard] Infer and print to logs client public key

[DanielBaulig]

Describe the problem you have/What new integration you would like

When configuring wireguard one provides the private key in the configuration, but there is no way to infer the corresponding public key without additional external tools like wireguard-tools' wg pubkey. It would be very useful if esphome could just infer the public key for the private key provided via config and print it to the logs.

Please describe your use case for this integration and alternatives you've tried:

When configuring a remote endpoint for a specific configured esphome node with wireguard i need to look up the node configuration, copy the private key and pipe it through wg pubkey.

Additional context

N/A