chore: reuse exception loader from kyverno

[eddycharly]

This PR reuses exception loader code from kyverno.

[codecov]

Codecov Report

Merging #501 (dc5dc1d) into main (3bfee7a) will decrease coverage by 1.32%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##             main     #501      +/-   ##
==========================================
- Coverage   16.57%   15.26%   -1.32%     
==========================================
  Files           9        9              
  Lines         573      570       -3     
==========================================
- Hits           95       87       -8     
- Misses        453      457       +4     
- Partials       25       26       +1     

Files Changed	Coverage Δ
backend/pkg/policy/load.go	70.96% <ø> (ø)
backend/pkg/resource/load.go	46.66% <46.66%> (ø)
backend/pkg/server/api/engine/request.go	46.15% <100.00%> (ø)

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