chore: Add auto-prune tests + fix namespace autoprune policy UI issue (PROJQUAY-6773)

[harishsurf]

• Adds more repository auto-prune tests
• Fixes UI issue: when user is not an admin, the namespace autoprune policy under repository auto-prune policies tab shouldbe hidden

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.79%. Comparing base (74fd23d) to head (b2692e0).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2717   +/-   ##
=======================================
  Coverage   70.79%   70.79%           
=======================================
  Files         436      436           
  Lines       40526    40526           
  Branches     5283     5283           
=======================================
+ Hits        28690    28691    +1     
- Misses      10159    10160    +1     
+ Partials     1677     1675    -2     

Flag	Coverage Δ
unit	70.79% <ø> (+<0.01%)	⬆️

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[bcaton85]

LGTM