Add cantools test setup

[marcelbuesing]

Goal is basically to test unpacking and packing against the c code that is generated by cantools using rust bindings. So basically the flow is:

• use the dbc example to generate c source using cantools
• use a bindgen setup to generate rust bindings
• compare the dbc-codegen packing and the cantools packing

[marcelbuesing]

Wow! Amazing work! I didn't even know this tool existed sweat_smile

Are the current test failures bugs in our code? If so, let's either add an #[ignore] and merge this PR; or merge the bitvec PR first (that should fix them I guess).

I commented on two tiny nits :)

Thanks for the review. Yeah well I hope cantools is correct, otherwise it doesn't make sense to use it, but I think it's fairly widely used. Not entirely sure yet about the tests and why the results differ, but it's also not the same currently on the bitvec branch.

Anyway I think it's probably a good idea to ignore the test output for now, merge it and then make fix the bitvec branch.

[killercup]

Sounds good! Merging :)