Use client-go for SMI collector

[peterbom]

Addresses #127

This is to take us one step further towards removing our reliance on the kubectl binary and parity between operating systems, making use of the KubeCommandRunner library dealing with Unstructured client-go types introduced in #178.

cc: @Tatsinnit, @SanyaKochhar

[codecov-commenter]

Codecov Report

Merging #179 (2039041) into master (07ca8cc) will decrease coverage by 0.05%.
The diff coverage is 80.00%.

@@            Coverage Diff             @@
##           master     #179      +/-   ##
==========================================
- Coverage   79.00%   78.94%   -0.06%     
==========================================
  Files          13       13              
  Lines         700      717      +17     
==========================================
+ Hits          553      566      +13     
- Misses         90       92       +2     
- Partials       57       59       +2     

Impacted Files	Coverage Δ
pkg/collector/smi_collector.go	79.10% <80.00%> (-0.90%)	⬇️

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[Tatsinnit]

👍 /lgtm, thanks, deferring to @SanyaKochhar for an eye ball please. thank you so much.