Use feature_priority for update entities

[TheJulianJES]

Proposed change

This introduces feature_priority for update entities.

Currently, there's an issue where both the update entity for the client OTA cluster and the one for the server OTA cluster are discovered. If there's both an in and out OTA cluster present on a device (endpoint), the unique_id will conflict, with no warnings logged. The client OTA entity class indirectly takes precedence due to definition order.

This PR changes that to have only one entity be truly discovered, making the priority more explicit: client, then server.
For all affected devices in our diagnostics, see: #683

Additional information

Note: We can also prefer the server OTA entity if that's better, without causing breaking changes in HA. The unique_id stays the same after all. But I don't know which one actually works on these devices. Client is generally the way to do it.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.51%. Comparing base (229df22) to head (4c598df).
⚠️ Report is 1 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #684   +/-   ##
=======================================
  Coverage   97.51%   97.51%           
=======================================
  Files          62       62           
  Lines       10949    10950    +1     
=======================================
+ Hits        10677    10678    +1     
  Misses        272      272           

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[puddly]

Looks good to me. I wonder: does the zigpy side even work with a server-side OTA cluster? I think both were kept because discovery in the past didn't really differentiate between the two.

[TheJulianJES]

Hmm, no idea. We reintroduced that swapped direction matching, so I guess it should..?
Eh, but not sure if it works from zigpy -> device?