Add ability to launch debug servers in a separate process

[valeros]

Currently, PlatformIO starts and communicates with debug servers via a PIPE which is configured directly in the GDB configuration .pioinit file, for example:

target extended-remote | "C:/.platformio/packages/tool-openocd/bin/openocd.exe" -c "C:/.platformio/packages/tool-openocd/bin/openocd.exe" -c "gdb_port pipe; tcl_port disabled; telnet_port disabled" -f "C:/.platformio/packages/tool-openocd/openocd/scripts/board/st_nucleo_f4.cfg"

This approach doesn't work with GDB v12 which apparently has a bug in parsing the debug server command that fails the entire debug session. It'd be great to have ability to launch a debug server in a separate process as a workaround for such cases.