feat: download egg as per the RHEL major version

[xiangce]

• Mulitple eggs will be provided on CDN for different RHEL releases
• Decide the egg name before downloading according to the current RHEL major version
• The orignial "insights-core.egg" is set as default
• Jira Card: RHINENG-12166

All Pull Requests:

Check all that apply:

• Have you followed the guidelines in our Contributing document, including the instructions about commit messages?
• No Sensitive Data in this change?
• Is this PR to correct an issue?
• Is this PR an enhancement?

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 75.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 77.14%. Comparing base (b88a6e8) to head (cb097b1).

Files with missing lines	Patch %	Lines
insights/client/__init__.py	75.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4266      +/-   ##
==========================================
- Coverage   77.15%   77.14%   -0.01%     
==========================================
  Files         762      762              
  Lines       41510    41516       +6     
  Branches     8773     8773              
==========================================
+ Hits        32027    32029       +2     
- Misses       8426     8430       +4     
  Partials     1057     1057              

Flag	Coverage Δ
unittests	77.13% <75.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

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