fix: graceful handling of unavailable sites/vehicles.

[carleeno]

This should fix a couple of related issues:

• Unexpected error fetching tesla_custom data: local variable 'response' referenced before assignment alandtse/tesla#324
• Integration fails to setup if site or car fails to respond during setup alandtse/tesla#315

If get_vehicle_data failed for a TeslaException that wasn't a 408, it would try to return an unassigned variable. Now it will re-raise that "unexpected" exception to let the caller handle it.

Additionally the calls for get_vehicle_data in generate_car_objects did not handle a vehicle being offline gracefully, and would fail the entire integration setup. The same was for generate_energysite_objects for a very similar reason.

Now if the vehicle/site data is unavailable during setup, the device will still be added with the data dict empty. Each of the car/site classes are designed to handle an empty data dictionary, so this should be fine. From what I can tell, it's not really possible to NOT add a device that's in the vehicle list or site list without refactoring a lot of controller.py.

All of these cases are logged as warnings, as they don't break anything, but would be unusual/unexpected.

[alandtse]

Please note that we still need a verb after the fix:. I know it's weird, but it's consistent with other stuff like feat:

[carleeno]

Please note that we still need a verb after the fix:. I know it's weird, but it's consistent with other stuff like feat:

ahh thanks, that makes sense