internal: Use AIRSPEC_VERSION file to specify airspec version

[xerial]

No description provided.

[codecov]

Codecov Report

Merging #3122 (241510e) into main (ca25718) will decrease coverage by 0.01%.
Report is 2 commits behind head on main.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3122      +/-   ##
==========================================
- Coverage   82.85%   82.84%   -0.01%     
==========================================
  Files         350      350              
  Lines       14723    14723              
  Branches     2447     2447              
==========================================
- Hits        12199    12198       -1     
- Misses       2524     2525       +1     

see 2 files with indirect coverage changes

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