Move kube2iam to a plugin

[davidmccormick]

Move kube2iam out of the core codebase and into its own plugin

[k8s-ci-robot]

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[codecov-io]

Codecov Report

Merging #1730 into master will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1730      +/-   ##
==========================================
+ Coverage   25.19%   25.21%   +0.02%     
==========================================
  Files          98       98              
  Lines        5017     5013       -4     
==========================================
  Hits         1264     1264              
+ Misses       3611     3607       -4     
  Partials      142      142

Impacted Files	Coverage Δ
pkg/api/types.go	0% <ø> (ø)	⬆️
pkg/api/cluster.go	0% <ø> (ø)	⬆️

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[davidmccormick]

@dominicgunn could you take a quick look? I've spun it up in a new cluster to test and looks ok.

[dominicgunn]

Looks great, also love the idea of moving all of this to a plugin.

[dominicgunn]

/lgtm