This bases on Iggy's st3m/st4m unification branch, and is the first
large step towards actually unifying st3m/st4m.

python_payload.py now passes typechecks!

However, I had to rip out touch-based scroll controller code (for now
left in comments) as I didn't exactly understand how it works. But I'll
come back to it later.

Current ctx seems to be broken for the simulator. This is an older
release, which doesn't have our newest fonts, but at least it kinda
works.

This update brings some fixes to excluding miniz from build and
enabling binary search for glyphs in the internal font engine.

Also make licensing clearer, ctx.h itself which is in this folder is
licensed under LGPLv3+, it is the micropython bindings - uctx which
live in ../micropython/usermodule/mp_uctx.c which are MIT licensed.

Short reads generally shouldn't happen, but let's be defensive there.

Instead, let's explicitly check the return code of i2s reads.

Brought to you by: “my interrupt didn't get initialized and i got very
confused”.

1. The page preview seems unusable anyway, as GitLab doesn't serve HTML
   pages (only allows to download them).
2. Rules seems broken and 'splits' pipelines:
   https://gitlab.com/gitlab-org/gitlab/-/issues/34756
   In return, 'only' is deprecated, but at least it works.

This also hopefully stops us from submitting random MR docs onto the
production pages.