chore: Remove usages of k8s.io/kubernetes (#4055)

[jMarkP]

Towards #4055 and #5173 (once argoproj/gitops-engine#205 and argoproj/gitops-engine#206 have been merged at least).

The argo-cd repo only has a few direct references to k8s.io/kubernetes:

• k8s.io/kubernetes/pkg/util/slice has been migrated to k8s.io/kubectl/pkg/util/slice
• k8s.io/kubernetes/pkg/api/v1/resource/PodRequestsAndLimits has a (AFAICS) functionally identical implementation in k8s.io/kubectl/pkg/util/resource (modulo a feature gate features.PodOverhead which I'm presuming is never set client side?)
• k8s.io/kubernetes/pkg/util/node/NodeUnreachablePodReason which is just a string constant and doesn't feel worth pulling in a whole package just to avoid a magic string usage. Especially as other repos under the kubernetes org already use the plain string instead of taking a code dependency.

I've run make build and make test on this change and it seems healthy.

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[codecov-io]

Codecov Report

Merging #5434 (0b97da5) into master (bb15a49) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master    #5434   +/-   ##
=======================================
  Coverage   40.94%   40.94%           
=======================================
  Files         137      137           
  Lines       18613    18613           
=======================================
  Hits         7621     7621           
  Misses       9905     9905           
  Partials     1087     1087           

Impacted Files	Coverage Δ
controller/cache/info.go	63.54% <0.00%> (ø)
server/account/account.go	69.16% <ø> (ø)

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[alexmt]

Thank you for the improvement and detailed PR description! LGTM