Keychron K*: restructure

[dexter93]

Major restructure of keychron keyboards layout.

• USB descriptors updated
• optical switch support
• common keymaps for each layout
• VIA enabled across all keymaps
• new structure is scalable for new revisions and variants
• ISO/ANSI is handled now
• K6 White is now using the C* matrix
• Debounce set to 5 by default

Description

Types of Changes

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

Issues Fixed or Closed by This PR

• Fixes [Bug] Keymap inconsistencies #174 [Bug] Keychron faking Apple Keyboard #152

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• 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).

[dexter93]

This still needs some cleanup for visuals, but it should be good for testing.

Note: VIA json's are missing for most of the keyboards still, and the ones that are there probably need USB descriptor updates for new VID/PID per device.

[dexter93]

Cleanup done. VIA functionality verified. Closing this ASAP since there are keyboard related PR's pending, so they can rebase accordingly