fix: add unique tag to test image to avoid collisions with other tests

[renzodavid9]

Fixes: #8025

Description
Add unique tag to test image to avoid collision with other tests running at the same time using the same image.

[codecov]

Codecov Report

Merging #8087 (a34604b) into main (290280e) will decrease coverage by 3.99%.
The diff coverage is 53.61%.

@@            Coverage Diff             @@
##             main    #8087      +/-   ##
==========================================
- Coverage   70.48%   66.48%   -4.00%     
==========================================
  Files         515      597      +82     
  Lines       23150    29172    +6022     
==========================================
+ Hits        16317    19395    +3078     
- Misses       5776     8338    +2562     
- Partials     1057     1439     +382     

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/credits/export.go	0.00% <0.00%> (ø)
cmd/skaffold/app/cmd/deploy.go	40.90% <0.00%> (-12.94%)	⬇️
cmd/skaffold/app/cmd/test.go	44.44% <0.00%> (ø)
cmd/skaffold/app/exitcode.go	100.00% <ø> (+6.66%)	⬆️
cmd/skaffold/skaffold.go	0.00% <0.00%> (ø)
cmd/skaffold/app/cmd/inspect_tests.go	62.50% <14.28%> (-1.14%)	⬇️
cmd/skaffold/app/cmd/render.go	35.48% <18.18%> (-5.90%)	⬇️
cmd/skaffold/app/cmd/lsp.go	28.12% <28.12%> (ø)
cmd/skaffold/app/cmd/run.go	64.28% <33.33%> (-9.63%)	⬇️
cmd/skaffold/app/cmd/fix.go	56.41% <37.50%> (-20.07%)	⬇️
... and 394 more

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