[Tests] Increase QMK test coverage take 2

[KarlK90]

This is a follow up to #13789 which was a bit rushed 😉

Description

This PR enhances the current unit-testing integration testing facilities and adds additional tests:

• All tests use an isolated per-test keymap instead of a global shared keymap in keymap.c the usage goes like this:

/* Define keys like this: layer, column, row, keycode */
auto       key_a      = KeymapKey(0, 0, 0, KC_A);
auto       key_lshift = KeymapKey(0, 1, 1, KC_LSFT);

/* Add keys to keymap for this test */
set_keymap({key_a, key_lshift});

key_a.press();
key_a.release();
key_lshift.press();
key_lshift.release();

• Tests that fail provide a lot more context on the events that happened during the execution.
• Tests were added:
  • basic key-presses
  • mod-taps and layer taps with different tap-hold configurations
  • one-shot mods and layers

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).

[KarlK90]

Not sure why the formatters had a hickup...