Use Numpy for all revisions

[hchargois]

Extend the use of numpy for serializing the image data of revisions B, C and D. Cf. #319

I've added tests to make sure the new serialization results in exactly the same calls to the serial interface as before. The tests can be run like this: python -m unittest from the root directory.

The tests can also be used as simple benchmarks (in that case the assertions are not checked) like this:

BENCHMARK=1 python -m unittest

On my machine, the benchmark results are as follows (before -> after)

• Rev B: 0.56 s -> 0.009 s (~ 60x speedup)
• Rev C: 1.45 s -> 0.036 s (~ 40x speedup)
• Rev D: 0.36 s -> 0.015 s (~ 20x speedup)

This PR is based off of #622 so ideally that one should be merged before this one.

[hchargois]

Rebased on top of main now that #622 is merged

[mathoudebine]

Thank you @hchargois much easier to read!
I will take some time to test it with the different displays before merging it