* Simplify nest event handling
Use device specific update callbacks rather than a global callback.
The motivation is to prepare for a follow up change that will store
camera specific event tokens on the camera itself, so that a service
can later fetch event specific image snapshots, which would be difficult
to send across the event bus.
* Increase nest camera test coverage
* Remove unnecessary device updates for nest cameras
* Remove unused imports
* Fix device id check to look at returned entry
* Remove unused imports after rebase
* Partial revert of nest event simplification
* Push more update logic into the nest library
* Revert nest device_info changes
* Revert test changes to restore global update behavior
* Bump nest library version to support new callback interfaces
