Conbee III support

[puddly]

Depends on zigpy/zigpy#1281 to filter out extraneous ZDO endpoint in 0x26450900.

I'm targeting all available firmware versions for this device for this PR. Endpoint 0 being present in the simple descriptor response for the first firmware version will require a bugfix in zigpy.

To test:

pip uninstall zigpy zigpy-deconz
pip install 'git+https://github.com/puddly/zigpy-deconz@puddly/conbee-iii'
pip install 'git+https://github.com/puddly/zigpy@puddly/ignore-ep-0-descriptor'

[xxLeoxx93]

I assume these 3 lines are required if I want to use the Conbee 3 already?
When I use docker I propably have to do this after each pull?

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (7264e6a) 98.76% compared to head (e56caad) 98.51%.

Files	Patch %	Lines
zigpy_deconz/zigbee/application.py	94.23%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #232      +/-   ##
==========================================
- Coverage   98.76%   98.51%   -0.26%     
==========================================
  Files           7        7              
  Lines         894      877      -17     
==========================================
- Hits          883      864      -19     
- Misses         11       13       +2     

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