[v0.0.21] Adopt new K8s ext API to contribute openshift nodes to the tree

[dgolovin]

Fix #852, #851.

[codecov]

Codecov Report

Merging #849 into 0.0.21 will decrease coverage by 1.77%.
The diff coverage is 30.76%.

@@            Coverage Diff             @@
##           0.0.21     #849      +/-   ##
==========================================
- Coverage   94.76%   92.98%   -1.78%     
==========================================
  Files          23       23              
  Lines        1376     1412      +36     
  Branches      222      233      +11     
==========================================
+ Hits         1304     1313       +9     
- Misses         72       99      +27

Impacted Files	Coverage Δ
src/extension.ts	76.98% <30.76%> (-20.8%)	⬇️

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