Changed the endpoints code to rename the existing endpoint types to
"transport" and add the concept of "endpoint instances". A transport is
the method by which data is sent, while instances allow describing
multiple endpoints that use the same transport (e.g. bluetooth profiles)
Also added new APIs to get the total number of possible endpoint
instances and assign each instance a unique index, which can be used
for tracking separate state for each endpoint in other code files.
* 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.
