Stop-gap forward-port Drop LED features for CTRL and ALT

[just-another-jxliu]

Description

Forward-port of LED features from Massdrop QMK fork:

• Mode that turns off every other edge LED
• Ability to decrease brightness of only edge LEDs
• Ability to set the ratio of key to edge LED brightness (unused by keymap)
• Added up/down, radial inward/outward LED pattern directions
• Factory debug mode

Updates the following keymaps to add keys using the above feature set:

• massdrop/alt/default_md
• massdrop/alt/mac_md
• massdrop/ctrl/default_md
• massdrop/ctrl/mac_md

This is a stop-gap change while a larger rework of QMK support for the current generation of Drop keyboards is in progress.

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

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).