Removed the label property from built-in behaviors, custom behaviors
defined in a few keymaps, and macros generated with ZMK_MACRO().
Now that node names are used to identify behaviors, and names only need
to be unique within the set of behaviors, the names of all behaviors
have been shortened to be similar to their original labels.
This means that any keymaps which reference behavior nodes by name
instead of by label will need to be updated. Keymaps typically use the
labels though, so most keymaps should be unaffected by this change.
To combine multiple sticky modifiers, the sticky keys must ignore
other (sticky) modifier keypresses.
This behavior is important for "callum-style mods", where all modifiers
are sticky mods.
Fixes#829
* 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.
