Implement HID keyboard mode

[ASleepyCat]

Closes #86.

Keyboard mode has support for HID lighting. HID and keyboard inputs cannot be enabled at the same time, although this can be changed fairly easily if someone wants both inputs sent at the same time.

Due to button restrictions (IIDX back-compat and SDVX only having nine and seven buttons respectively), I've made input mode switching performable only on boot.

Buttons and analog mappings will need to be rebinded in spicecfg, etc. after this is merged.

Major refactoring in general:

• Add support for keyboard input for IIDX and SDVX
  • IIDX only uses keyboard inputs, SDVX has keyboard and mouse inputs
  • Add HID interfaces for keyboard and mouse input data
    • Each interface can only support one IN and OUT endpoint, so having keyboard and mouse support requires multiple interfaces (at least on our MCU, not sure if this a USB HID or AVR limitation)
• Remove most function pointers for update calls, replace them with classes
• Rename analog_turntable to analog_button since it's also used for SDVX knobs
• Removed function pointers for CALLBACK_USB_GetDescriptor(), instead assign some global variables
• Renamed some enums from SCREAMING_SNAKE_CASE to PascalCase
• Change FIXED_CONTROL_ENDPOINT_SIZE and HID_EPSIZE to 64
• Enable INTERRUPT_CONTROL_ENDPOINT
• Cleaned up HID report descriptors a little
• Ignore button inputs if pressed after boot
  • This is mainly to prevent keyboard inputs being sent when inputting a boot combo
• Fix LR2 compatibility (closes Lunatic Rave 2 not working with beefboard anymore #89)
  • LR2 expects both X and Y axis to be present
• Fix X and Y axis in SDVX joystick report descriptor being flipped
• Suppress some warnings in fastled_shim.h

[HWXLR8]

Thanks for the huge effort. Code looks good. I don't want to introduce more variables into the mix, so I will defer merging until we have the TT issues sorted.

[HWXLR8]

On second thought, I will merge since your optimization pass PR is based off the same branch. I am an idiot, I stopped reading at "keyboard-mode"