Use download artifact instead

[ciarams87]

Proposed changes

Problem: After the secure build workflow changes, on main or production runs the build binary job was running on a different runner type from the helm tests job meaning the cache doesn't work correctly between these stages.

Additionally, the nightly run attempts to log in to the NGINX image registry using the actor of the pipeline. This has been failing as the actor of the scheduled builds no longer works here.

Solution: Use artifact upload and download instead of cache for the binary so it persists across runner types, and edit the schedule line with a comment so that I appear as the actor for the nightly runs instead

Closes #4032

Checklist

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• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

Release notes

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please add a brief note that summarizes the change.

NONE

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.69%. Comparing base (2d2dfa8) to head (53af29c).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4033      +/-   ##
==========================================
- Coverage   86.71%   86.69%   -0.02%     
==========================================
  Files         128      128              
  Lines       16758    16758              
  Branches       62       62              
==========================================
- Hits        14531    14529       -2     
- Misses       2043     2044       +1     
- Partials      184      185       +1     

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