[XAP] add binding for dynamic keymap

[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.

Add support for routes to exercise the dynamic keymap subsystem, matching VIA capabilities.

• Assumption is that the data received by the command handlers will already be transformed into numeric QMK keycodes
  • We aren't going to send "set layer 0 matrix {0,2} to S(C(KC_F1))" and let the firmware parse the value
  • Equivalent will be post-transform (as per keycode.json) 0x04 0x00 0x00 0x02 0x03 0x99 or whatever the values come out to be
• Virtually all the logic is in place already in the current dynamic_keymap.c, just a case of invoking the APIs as per the command definitions
• Macros have been de-scoped to [XAP] add binding for dynamic macros #16797