Support for execution of asynchronous target, such as openocd, which
by default runs in the background, but if it's the only target idf.py
outputs the openocd in the console waiting for termination by user.
Supports also blocking commands gdb and gdbtui to start a debugging
session in an active console.
Supports running gdbgui running a UI debugging session in a browser
window, using the active console for other commands, such as openocd
or monitor.
Supports combining the debug targets in one action list, such as
idf.py openocd gdbgui monitor
The old command caused was incorrect (x is “examine”, not “execute”)
and caused GDB register update only by chance. This replaces it with
“flushregs” command which purpose is exactly that — force GDB to
fetch registers from the remote.
