Extend lint checks to reject duplication of defaults

[zvecr]

Description

Example output:

qmk lint -kb all 2>&1 | grep "duplicates default value" | grep rgb_matrix
☒ adm42/rev4: Option "rgb_matrix.led_flush_limit" duplicates default value of "16"
☒ ashwing66: Option "rgb_matrix.led_flush_limit" duplicates default value of "16"
☒ cipulot/ec_980c: Option "rgb_matrix.max_brightness" duplicates default value of "255"
☒ eek/silk_down: Option "rgb_matrix.led_flush_limit" duplicates default value of "16"
☒ eek/silk_up: Option "rgb_matrix.led_flush_limit" duplicates default value of "16"
☒ ein_60: Option "rgb_matrix.led_flush_limit" duplicates default value of "16"
☒ fs_streampad: Option "rgb_matrix.default.animation" duplicates default value of "cycle_left_right"
☒ geekboards/macropad_v2: Option "rgb_matrix.default.sat" duplicates default value of "255"
☒ handwired/hnah40rgb: Option "rgb_matrix.led_flush_limit" duplicates default value of "16"
☒ marcopad: Option "rgb_matrix.default.val" duplicates default value of "255"
☒ mechboards/crkbd/pro: Option "rgb_matrix.default.animation" duplicates default value of "cycle_left_right"
☒ mechboards/lily58/pro: Option "rgb_matrix.default.animation" duplicates default value of "cycle_left_right"
☒ mechboards/sofle/pro: Option "rgb_matrix.default.animation" duplicates default value of "cycle_left_right"
☒ momokai/aurora: Option "rgb_matrix.default.hue" duplicates default value of "0"

TODO:

• Work out what defaults to cover in this first pass

Types of Changes

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