Unit tests

[woodruffw]

It'd be nice to have some basic tests in the CI, probably using mishegos's manual mode to feed some simple inputs in.

[woodruffw]

To elaborate: we probably want simple valid instruction samples to test with, just to ensure that every decoder reports correctly. Even just some NOPs and simple MOVs would probably suffice.

[ekilmer]

This would be nice to catch simple runtime issues like missing symbols, even if the workers seem to build correctly (relevant PR for bddisasm bitdefender/bddisasm#53, but this could have easily been any other tool)

[woodruffw]

Yep! It should be very easy to write a basic self-test, since it's just:

M=1 mishegos ./workers.spec <<< "90" > /dev/null

...or something similar, where 90 is the hex string for the instruction to test all of the workers against.