Migrate from MaixPy to MicroPython

[ghost]

Move away from Sipeed's custom MaixPy fork of MicroPython so that the project won't be so tightly tied to the M5StickV / M5Stack.

The longer-term goal here is to move Krux toward platform independence so that eventually it could run on any of MicroPython's supported architectures

EDIT: I think there are two ways to approach this: 1) add shims to ports to give them a "maixpy-like" set of modules that Krux can use, or 2) find a way to add shims to MaixPy so that Krux code can be rewritten to rely on standard micropython modules.