Add 'Enter manually' as an item into the popup menu. If that is the
chosen option the text field is enabled. If the user chooses a serial
port from the list the text field is disabled and the configuration
will be updated with the value from the list.

List serial ports using three methods:
- /dev/serial/by-id
- /dev/ttyOP_*
- using serialport module

OpenPlotter 2 has a serial port manager that allows the user to
rename serial ports with symbolic names using udev rules. On Linux
there are already persistent names unde by-id and lastly serialport
works on at least MacOS and hopefully on Windows as well.

Change payload to contain lists of serialports for
the different listing methods and show them in the
popup menu  with separators.