* Make NextBus coordinator more resilient and efficient
Resolves issues where one request failing will prevent all agency
predictions to fail. This also removes redundant requests for
predictions that share the same stop.
* Add unload entry test
* Prevent shutdown if the coordinator is still needed
* Refactor NextBus integration to use new API
This removes the `messages`, `directions`, and `attribution` attributes
from the sensor. Those may be added back in the future with additional
refactoring.
Some existing sensors may be broken today because of deprecated Agency
names. This patch will not migrate them as the migration path is
ambiguous. Setting up again should work though.
* Move result indexing outside of try/except