* Use lesser-known DT features to skip behaviors not referenced
in the user keymap
* Update the behaviors to skip code if no nodes found.
* Remove some empty config/data structs where unused in
behaviors.
* 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.
