* Simplify the `bt` behavior to one current command
`BT_CLEAR_BONDS_CMD`.
* Simplify BLE code for split and non-split keyboards.
* Remove keymap processing from split peripheral side.
* Add `bt` behavior that can be used to perform certain actions,
such as next/prev identity, reset identity, etc.
NOTE: Multiple identities is only supported for non-split shields,
due to missing Zephyr identity functionality for dual
central/peripheral devices.
* Proper bond reset tied to action, that honors peripheral bonds,
so folks can reset and pair to other hosts, without breaking
bonds between splt halves.
* Especially for splits, we need the ability to
unpair all paired devices as sledgehammer
if we need to "reset things", and doing so via
keymaps isn't suitable.
* Allows shields to define a collection of key
positions that if all held 2 seconds after
startup, will unpair all existing pairs for the
device.
