use kubectl's built-in kustomize when possible

[nkubala]

Fixes #1781 

this adds logic to check if a user's kubectl version is greater than 1.14, and if so uses the built-in kustomize command. this removes the hard dependency on an external kustomize binary for all but the oldest kubectl versions.

[codecov]

Codecov Report

Merging #4183 into master will increase coverage by 0.05%.
The diff coverage is 100.00%.

Impacted Files	Coverage Δ
pkg/skaffold/deploy/kubectl/cli.go	91.30% <100.00%> (+0.39%)	⬆️
pkg/skaffold/deploy/kustomize.go	76.21% <100.00%> (+1.50%)	⬆️
pkg/skaffold/runner/logger.go	100.00% <0.00%> (ø)
pkg/skaffold/runner/dev.go	65.38% <0.00%> (+0.26%)	⬆️
pkg/skaffold/runner/build_deploy.go	57.29% <0.00%> (+1.16%)	⬆️
pkg/skaffold/util/cmd.go	52.38% <0.00%> (+4.76%)	⬆️

[balopat]

LGTM, awesome!

[briandealwis]

Would it make sense to use a kustomize binary if found, and otherwise try kubectl kustomize?

[pickfire]

Would it make sense to use a kustomize binary if found, and otherwise try kubectl kustomize?

No, it doesn't make sense. It should be using kubectl kustomize even though kustomize binary is found, kustomize binary is useless since it does not work with existing kubectl kustomize, there is a breaking change.