Custom LED implementation

[FeralAI]

This is the firmware implementation for #107.

This PR requires OpenStickCommunity/WebConfigurator#38 for the UI updates.

A new animation mode for Custom Theme has been added. If enabled, this mode will use the new CustomTheme and CustomThemePressed animation subclasses and configured LED options to display a customized static theme with customized button color presses, as the issues requested.

In the process of debugging I reworked how the pressed animation is created since it was only created as a fallback instead of when needed like the base animations.

If we want to do any customized themes with animations that will require a larger refactor or migration of the LED controller library.

[FeralAI]

This should be functionally ready now. Summary of changes not directly related to this feature:

• Fixed excessive memory use in webconfig.cpp when deserializing POST data
• Bumped stack size up to 4kb with add_compile_definitions(PICO_STACK_SIZE=0x1000) in CMakeLists.txt
• Updated ArduinoJson library to v6.21.2
• Fixed issue where user couldn't use the Previous Animation shortcut to cycle around the animation list (needed explicit cast to check for negative)
• Pressed animations are now properly created and destroyed like normal animations
• Pressed animations should flicker much less when changing animations

I'll add documentation for this feature over the weekend.

[arntsonl]

Super cool!! With fluppi's changes, we'll have better stack space and fully independent LED configurations!