chore: use cmp.Diff to check for differences

[briandealwis]

Produce more readable test failures by using cmp.Diff.

time="2022-09-27T19:29:55Z" level=info msg="Pods marked as ready: map[module1:true module2:true]" subtask=-1 task=DevLoop
    build_test.go:257: Platforms differ (-got,+want):
          []v1.Platform(Inverse(cmpopts.SortSlices, []v1.Platform{
        - 	{Architecture: "amd64", OS: "linux"},
          	{Architecture: "arm64", OS: "linux"},
          }))

[codecov]

Codecov Report

Merging #7896 (501bac1) into main (290280e) will decrease coverage by 3.82%.
The diff coverage is 53.94%.

@@            Coverage Diff             @@
##             main    #7896      +/-   ##
==========================================
- Coverage   70.48%   66.65%   -3.83%     
==========================================
  Files         515      593      +78     
  Lines       23150    28698    +5548     
==========================================
+ Hits        16317    19130    +2813     
- Misses       5776     8160    +2384     
- Partials     1057     1408     +351     

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/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%)	⬇️
cmd/skaffold/app/cmd/verify.go	41.17% <41.17%> (ø)
... and 365 more

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