feat: Enable CSP with nonce for Helix 4

[andreituicu]

Backport of #773 for Helix 4. More details in the original PR.

[github-actions]

This PR will trigger a minor release when merged.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (3d6efbc) to head (0a1a97b).
Report is 55 commits behind head on 5.x.

Additional details and impacted files

@@            Coverage Diff             @@
##               5.x      #811    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files           50        51     +1     
  Lines         4539      4785   +246     
==========================================
+ Hits          4539      4785   +246     

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