* Modify test to account for scenario of unknown unsupported attributes
* Add error checking for finding unsupported attributes
* Change comment to clarify zigpy misses an attribute def
This should make it more clear that it's about an unknown attribute (where zigpy doesn't have an attribute definition).
* Increase test coverage
This increases test coverage by doing the following:
- adding the `IasZone` to our test device, so we have a cluster which actually has some attribute definitions
- adding not just an unknown unsupported attribute by id, but also by name
- adding a known unsupported attribute by id and by name
* Fix diagnostics logic
5d0c8947a1