HIL: add a pyocd flasher, flash lpcxpresso55s28 over CMSIS-DAP (#4094)

pyocd has no VID/PID probe filter, so test/hil/pyocd/run_pyocd.py restricts pyusb discovery to the roster's vid_pid; user_script.py does an LPC55 debug-mailbox reset before pyocd's reset catch, whose flash blank check fails above 100 MHz (UM11126 5.3).