util: read index.json for snapshot package feeds

[efahl]

As of the apk switchover, the Packages file no longer is created as part of the package feeds. Instead, utilize the index.json file created from apk's packages.db.

See openwrt/openwrt@f841870

[codecov]

Codecov Report

Attention: Patch coverage is 25.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 90.39%. Comparing base (5e65dec) to head (8e65fef).
Report is 149 commits behind head on main.

Files with missing lines	Patch %	Lines
asu/main.py	0.00%	4 Missing ⚠️
asu/util.py	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1080      +/-   ##
==========================================
+ Coverage   80.75%   90.39%   +9.63%     
==========================================
  Files          15       14       -1     
  Lines         977     1114     +137     
==========================================
+ Hits          789     1007     +218     
+ Misses        188      107      -81     

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[aparcar]

Some time ago I implemented this to always try index.json first and fallback to Packages if not available. I think the issue with the your approach was something with the ABI version, did you check for that?

[efahl]

Yeah, the ABI versioned names are currently present in the index.json files (which is why I restricted this to use index.json for snapshots, and Packages for all the "old" builds). @Ansuel and I have discussed the ABI issue a bit on the forum, but it's an upstream issue and this gets the pipeline in place for the APK builds. Once ABI-ed names issue gets resolved upstream, this should work without modification.