[jtag] Add mi mode flag (RDT-290)

[hfudev]

For now we're using string mode for gdb by default. there're two ways to support mi2 mode

1. run gdbmiparser.parse_response to parse the output
2. use gdbmi = GdbController() instead of bare subprocess.popen

Prefer to use the first one. make the gdb write blocking as well, like the openocd one.

[hfudev]

a few reasons not use GdbController directly

1. esp-idf only support pygdbmi 0.9.0.2. which has issue: Suppress logging output from StringStream? cs01/pygdbmi#36. This issue is fixed in 0.9.0.3, but the version is not compatible with gdbgui==0.13.2.0
2. somehow break the philosophy a bit. the write is blocking the IO.

[hfudev]

https://pypi.org/project/esp-debug-backend/