Add coverage calculation and badge

[skirtan1]

Which problem is this PR solving?

Enhancements for #6572

Description of the changes

• Use retry upload action from main branch
• Delete lines for model.pb.go from coverage
• add badge to readme

How was this change tested?

Checklist

• I have read https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
• I have signed all commits
• I have added unit tests for the new functionality
• I have run lint and test steps successfully
  • for jaeger: make lint test
  • for jaeger-ui: npm run lint and npm run test

[yurishkuro]

@skirtan1 I think you will need to go back to your initial version of using a sub-action, because the workflow is failing with an error which I think is not solved in the retry-action (according to Wandalen/wretry.action#115)

[yurishkuro]

I don't understand why it fails here

but works fine in the jaeger repo

[yurishkuro]

let's try with 3.7.0

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.85%. Comparing base (3e525d7) to head (1f563c0).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##            main     #127       +/-   ##
==========================================
+ Coverage   8.33%   87.85%   +79.51%     
==========================================
  Files         16       12        -4     
  Lines       7830      568     -7262     
==========================================
- Hits         653      499      -154     
+ Misses      7135       67     -7068     
+ Partials      42        2       -40     

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[yurishkuro]

Thanks!