[modm_tools] GDB with OpenOCD backend does not work on Windows

[salkinium]

There are two issues:

1. AttributeError: module 'os' has no attribute 'setsid' and AttributeError: module 'os' has no attribute 'killpg'. We use these to start and kill the OpenOCD process in the background of GDB. No clue how to fix that.
2. /dev/null does not exist on Windows, however that can easily be fixed:

   if silent:
       null_file = "nul" if "Windows" in platform.platform() else "/dev/null"
       commands.append("log_output " + null_file)

[salkinium]

I "fixed" running OpenOCD in the background on Windows only to discover that arm-none-eabi-gdb does not support TUI mode on Windows and gdbgui dropped Windows support recently due to lack of gevents support.

I'm not sure how to fix this.