Add ezspVersion to network backup metadata

[Copilot]

Add ezspVersion to the internal backup metadata. Z2M will not load zigpy backups otherwise.

[puddly]

@copilot Add the following comment to the newly-added code in load_network_info: Z2M will not load EZSP backups without this internal key.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.52%. Comparing base (cdd1217) to head (ed11a47).
⚠️ Report is 1 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #693   +/-   ##
=======================================
  Coverage   99.52%   99.52%           
=======================================
  Files          58       58           
  Lines        3971     3971           
=======================================
  Hits         3952     3952           
  Misses         19       19           

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[Copilot]

@copilot Add the following comment to the newly-added code in load_network_info: Z2M will not load EZSP backups without this internal key.

Done in ed11a47. Added the comment explaining that Z2M will not load EZSP backups without this internal key.