This should be purely an implementation change,
for end users there should be no functional difference.
The entire key configuration is in one file with ~5000 lines of code.
Mostly avoiding code duplication and preserve comments and utility
functions from the C code.
It's a bit long but for searching and editing it's also convenient to
have it all in one file.
Notes:
- Actual keymap is shared by blender / blender_legacy
and stored in `keymap_data/blender_default.py`
This only generates JSON-like data to be passed into
`keyconfig_import_from_data`, allowing other presets to load and
manipulate the default keymap.
- Each preset defines 'keyconfig_data'
which can be shared between presets.
- Some of the utility functions for generating keymap items still
need to be ported over to Python.
- Some keymap items can be made into loops (marked as TODO).
See: D3907
