Allow for ChibiOS 20.x (master), as well as ChibiOS-Contrib imports

[tzarc]

Description

• Adds support for compiling against ChibiOS master branch
• Allows for automatic inclusion of the ChibiOS-Contrib source if there's a halconf_community.h present (or if USE_CHIBIOS_CONTRIB = yes is added to rules.mk)
• Misc cleanup with leftover irrelevant files

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[tzarc]

Rebased so the new syscalls change isn't required.

[tzarc]

Ideally, the testing would include the handwired/onekey/teensy_32 and handwired/onekey/teency_lc, as they're really the only two boards affected by this change.
For any other ChibiOS-based board, it's not going to see much difference, if any.