* Reference combos by index, not 32-bit pointers, and store bitfields
instead of arrays in several places, to bring down our flash/RAM usage.
* Use bit field to track candidate combos, to avoid needing an explicit
`ZMK_COMBO_MAX_COMBOS_PER_KEY` setting.
* Determine the max keys per combo automatically from the devicetree,
so we remove the ZMK_COMBO_MAX_KEYS_PER_COMBO Kconfig symbol.
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