Aligns *.h and *.c to underscore naming convention.

These were kept (with warnings) for backwards compatibility with external boards/shields:
- kscan-mock.h
- matrix-transform.h
They should be removed in the future.

PR: #523

Replaced with RegExp: /(?<!const )(struct device \*)/g

See: https://docs.zephyrproject.org/latest/releases/release-notes-2.4.html
PR: #467

Ran all the default keymaps through the keymap upgrader and manually adjusted
alignment.

* Use the LLVM style
* Override indent width (8) and column limit (100)
* Fixes #142.