feat(plugins/plugin-iter8): added new iter8 plugin

[starpit]

Iter8 documentation: https://iter8.tools/

Four new commands:

• iter8 metrics
• iter8 create experiment
• iter8 about
• iter8 config

Fixes #5400
Closes #5388

Description of what you did:

My PR is a:

• 💥 Breaking change
• 🐛 Bug fix
• 💅 Enhancement
• 🚀 New feature

Please confirm that your PR fulfills these requirements

• Multiple commits are squashed into one commit.
• The commit message follows Conventional Commits, which allows us to autogenerate release notes; e.g. fix(plugins/plugin-k8s): fixed annoying bugs
• All npm dependencies are pinned.

[codecov]

Codecov Report

Merging #5401 into master will decrease coverage by 0.07%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #5401      +/-   ##
==========================================
- Coverage   59.15%   59.08%   -0.08%     
==========================================
  Files          78       78              
  Lines        2544     2544              
  Branches      629      629              
==========================================
- Hits         1505     1503       -2     
- Misses        794      796       +2     
  Partials      245      245              

Impacted Files	Coverage Δ
packages/core/src/core/userdata.ts	63.88% <0.00%> (-4.17%)	⬇️
packages/core/src/core/command-tree.ts	62.05% <0.00%> (+0.44%)	⬆️

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