Add _detect_available_configs to serial_can

[josko7452]

Hi I am using serial_can interface and I was missing the serial port detection.

This is very simple PR, it just adds pySerial list_ports.comports() call non-intrusive way.
I.e. if the detection fails (or serial.tools.list_ports is not available) for one reason or another it just gives an empty list.
It does not attempt to get more detailed configuration (e.g. baudrates) besides the list of serial ports.

Tested on Linux and Windows:
Linux:

>>> can.detect_available_configs('serial')
[{'interface': 'serial', 'channel': '/dev/ttyUSB0'}]

Window:

>>> can.detect_available_configs('serial')
[{'interface': 'serial', 'channel': 'COM4'}]

As you'd expect. These configs can be directly used to connect to the interface (with the default baudrate of the serial interface).

[codecov]

Codecov Report

Merging #811 into develop will increase coverage by 0.14%.
The diff coverage is 84.61%.

@@             Coverage Diff             @@
##           develop     #811      +/-   ##
===========================================
+ Coverage    69.71%   69.85%   +0.14%     
===========================================
  Files           70       70              
  Lines         6577     6578       +1     
===========================================
+ Hits          4585     4595      +10     
+ Misses        1992     1983       -9     

[hardbyte]

Thanks for the contribution :-)

[felixdivo]

Really cool and simple! Thanks!

[felixdivo]

I'll just wait until the CI tests pass and merge it afterwards.