[Core] Feature: Add Key interrupt

[Xelus22]

Description

TODO: ADD DOCS

(Also open to different naming suggestions)

This adds a feature where it is a key interrupt and forces another key to be un-pressed when one key is pressed.

Usage: keymap.c

#ifdef KEY_INTERRUPT_ENABLE
const uint16_t PROGMEM key_interrupt_list[][NUM_INTERRUPT_KEYCODES] = {
    [0] = {KC_D, KC_A},
    [1] = {KC_A, KC_D}};
#endif

This example shows on the first interrupt pair, when D is held, A will be interrupted and unpressed. The second interrupt pair is when A is held, D will be unpressed. This means that A and D can never be in the same packet (from a normal keystroke).

Types of Changes

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

Issues Fixed or Closed by This PR

• Add new feature key interrupt

Checklist

• [x] My code follows the code style of this project: C, Python
• [x] I have read the PR Checklist document and have made the appropriate changes.
• [x] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [x] 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).