add explicit error codes for various config parsing errors

[gsquared94]

Fixes #5412

This PR adds specific failure error codes and appropriate suggestion text via ActionableErrors for skaffold's config parsing step.

[codecov]

Codecov Report

Merging #5483 (e173475) into master (2cc744d) will increase coverage by 0.18%.
The diff coverage is 92.92%.

@@            Coverage Diff             @@
##           master    #5483      +/-   ##
==========================================
+ Coverage   71.46%   71.65%   +0.18%     
==========================================
  Files         398      399       +1     
  Lines       14641    14739      +98     
==========================================
+ Hits        10463    10561      +98     
  Misses       3402     3402              
  Partials      776      776              

Impacted Files	Coverage Δ
pkg/skaffold/parser/config.go	78.68% <46.66%> (ø)
cmd/skaffold/app/cmd/runner.go	60.71% <100.00%> (+0.71%)	⬆️
pkg/skaffold/schema/errors/errors.go	100.00% <100.00%> (ø)

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[MarlonGamez]

hey @gsquared94 , my PR that separates enum definitions into their own file got merged, would you be able to move your enum definitions into proto/enums/enums.proto?