Add mullvad debug relay enable|disable commands

[MarkusPettersson98]

Implement new debug commands: relay disable and relay enable

Add two new mullvad debug subcommands:

• mullvad debug relay enable <country|city|hostname|openvpn|wireguard>
• mullvad debug relay disable <country|city|hostname|openvpn|wireguard>

These commands are used to update the state of relays the current relay list. This is useful to mock relays going offline or coming online from an offline state.

These new debug commands were conceived during the development of the feature for adding warnings for the upcoming OpenVPN deprecation, as there wasn't a convenient way of mocking this.

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This change is 

[hulthe]

Reviewed 6 of 6 files at r1, all commit messages.
Reviewable status: all files reviewed, 3 unresolved discussions

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mullvad-cli/src/cmds/debug.rs line 22 at r1 (raw file):

    Disable { relay: String },
    /// (Re)Activate this relay
    Enable { relay: String },

⛏️ Maybe mention that relay can be city/country/hostname/protocol? I would never guess that last one heh

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mullvad-cli/src/cmds/debug.rs line 58 at r1 (raw file):

                let mut rpc = MullvadProxyClient::new().await?;
                rpc.disable_relay(relay.clone()).await?;
                println!("Disabled relay {relay}");

⛏️ "Disabled relay se" or "Disabled relay wireguard" sounds a little weird, but w/e. It's just for debugging.

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mullvad-daemon/src/lib.rs line 3096 at r1 (raw file):

    // Debug features

    /// Mark [relay] as inactive in the daemon's relay list.

should probably say "active or inactive" or something