[XAP] finalise firmware-side binding generation

[tzarc]

XAP Task Info

Original Issue
Original spec document
Current XAP Definitions
Current XAP Generated Docs
Placeholder PR

Description

Any work in this area needs to be discussed with QMK Collaborators first, and in this case primarily with @tzarc due to their prior work in this area.

Initial bindings for the firmware side of the XAP protocol are already implemented under quantum/xap/ in the xap branch of qmk/qmk_firmware.

Need to extend this to all scenarios defined by the protocol definitions in data/xap/, ensuring that any cases where items aren't enabled are removed from compilation via the preprocessor.