Moves the command argument parsing to hwi.py. Instead of each function
taking args and client, they now take client and whatever else they
need. hwi.py handles the conversion from args and client to the actual
arguments.
The trezor and keepkey emulators use the same port so they cannot
be run at the same time. To work around this, the emulators are
instead started and stopped before and after each test using
unittest's setUp and tearDown functions. However, other devices
which do not have conflicts can still be run at test suite creation
time. This is still done for the coldcard.
Furthermore, since the trezor and keepkey both create and use
emulator.img files in the current working directory, when they are
started, the working directory is changed to be the one containing
the emulator executable to avoid conflicting emulator.img files
