Move ezspVersion key to correct place for Z2M

[TheJulianJES]

This fixes an issue where the eszpVersion is not in the correct place for Z2M, leading to "Current backup file is not for EmberZNet" issues when starting Z2M with a zigpy coordinator_backup.json.

Currently, the ezspVersion lands in metadata.internal.ezsp when converted to the open coordinator Z2M backup format.
But it should directly be in metadata.internal instead. For us, that means we'll need to move it out from the ezsp key, directly into metadata, as that'll later become metadata.internal when converted to Z2M's backup format.

Follow-up to this PR/comment (though I missed this at the time):

• Add ezspVersion to network backup metadata #693 (comment)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.53%. Comparing base (e2fbda7) to head (b0cb5f5).
⚠️ Report is 1 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #701   +/-   ##
=======================================
  Coverage   99.53%   99.53%           
=======================================
  Files          58       58           
  Lines        4128     4128           
=======================================
  Hits         4109     4109           
  Misses         19       19           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.