Add support for receiving basic fragmented messages

[ThomasKulin]

I am not much of a developer but I have found your project to be very useful and would like to contribute a change that I made to implement fragmented message support. This likely needs to be expanded to respect the EzspConfigId.CONFIG_FRAGMENT_WINDOW_SIZE and EzspConfigId.CONFIG_FRAGMENT_DELAY_MS configuration parameters.

[puddly]

Interesting! Are fragmented frames something you're seeing with a consumer device, or is this a device that you're working on?

[ThomasKulin]

I haven't seen them used in any consumer device so far. This is for something relating to solar inverters where Zigbee is used for data collection. Some of the data packets are large enough to necessitate fragmentation. This code works for my specific application where the device fragment window size is set to 1 (requiring an ack for each transmitted fragment). I have no way of testing with other window sizes. Feel free to recommend changes and I'll gladly make them!

[puddly]

I left a few comments regarding the cleanup code. Let me know if you have any questions.

Thanks again!

[puddly]

For the failing CI, you can set up pre-commit to auto-format your code and point out issues that CI would detect:

pip install pre-commit
pre-commit install
pre-commit run --all-files

This will also run every time you make a new Git commit, for future changes.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.44%. Comparing base (bdb7374) to head (6f2fcc0).
Report is 4 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #669      +/-   ##
==========================================
+ Coverage   99.21%   99.44%   +0.22%     
==========================================
  Files          51       52       +1     
  Lines        3695     3761      +66     
==========================================
+ Hits         3666     3740      +74     
+ Misses         29       21       -8     

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