This implements a basic Python simulator for the badge. It currently
can't do much other than just displaying the main selection screen, as
it implements no inputs.

This refactors the build system to be more in line with the average
ESP-IDF project.

This means that:
  1. `idf.py` from the main directory now works
  2. Adding components, running menuconfig, etc. should now be trivial.
  3. We don't have to edit files in micropython/ports/esp32/....

Hopefully this is the first step to yeeting the micropython checkout
from source and just depending on a submodule instead.

This adds initial support for building on Nix(OS). It can be tested by
following the updated README.md. The result should be the ability to
build the firmware without having to download any other dependencies.