Use kubernetes client-go in a few places

[ewollesen]

In general, the EKS-Anywhere project has shelled out to kubectl to interact with the cluster's API. However, given that the EKS-A kubectl binary is run via a docker image, it can be slow. For cluster creation/teardown, this slowness is amortized and isn't nearly as noticeable. But for commands like "list packages" which should be rather fast, it's very noticeable.

So we're starting to use API client libraries where it makes sense to speed up these calls that are more interactive in nature, or where faster responses make sense.

There will be more commits of this nature in the near future. So if you see patterns here that you don't like, or think could be improved, now would be a great time to bring them up for discussion. :)

As a historical note, the choice to shell out to kubectl was made because it was planned that EKS-A would support more versions of kubernetes than the upstream project would, and it was thought that the ability to swap out executable versions to match the kubernetes version would be an easier or more flexible way to manage the differences when compared with linking to / using multiple versions of the client libraries. Whether or not that is true remains to be seen, but that fact is being used as guidance here, in that—at least at first—we will replace only calls that are stable and therefore less likely to change or require multiple library versions. (Like the list and get calls replaced here).

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[codecov[bot]]

Codecov Report

Merging #2897 (c4aaad4) into main (60fc46c) will increase coverage by 0.05%. The diff coverage is 87.75%.

@@            Coverage Diff             @@
##             main    #2897      +/-   ##
==========================================
+ Coverage   62.48%   62.54%   +0.05%     
==========================================
  Files         335      335              
  Lines       26995    27014      +19     
==========================================
+ Hits        16869    16897      +28     
+ Misses       8839     8833       -6     
+ Partials     1287     1284       -3     

Impacted Files	Coverage Δ
pkg/dependencies/factory.go	67.78% <68.42%> (+0.01%)	:arrow_up:
pkg/curatedpackages/bundle.go	84.88% <100.00%> (+17.44%)	:arrow_up:

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[ewollesen]

/hold

I'm seeing some issues when no KUBECONFIG is provided (thanks to @a-cool-train) that I need to get sorted before this merges.