Add support to connect via ser2net

[oliv3r]

Checklist

• I have filled out the template to the best of my ability.
• This only contains 1 feature request (if you have multiple feature requests, open one feature request for each feature request).
• This issue is not a duplicate feature request of previous feature requests.

Is your feature request related to a problem? Please describe.

With Python's pyserial library it should also be possible to use 'remote' serial ports.

This is quite useful if your radio is far away from your server, and you want to use ser2net to connect the serial port via the network (e.g. rp2040 based device).

In certain docker setups this may be preferred, to run an isolated ser2net container, and connect hass using ser2net.

Describe the solution you'd like

With my zigbee device I do exactly that, and in the serial port entry field I use 'socket://zha:18888'. The same ought to be possible using meshtastic, but it seems like the input check will not allow this.

Describe alternatives you've considered

Connecting via BLE requires removal of the pin; connecting via WiFi means wifi is needed, and is also done without authentication.

Additional context

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