chore: add Kubernetes Copyright headers to all files

[myan9]

Fixes #7061

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.

[starpit]

lgtm!

[codecov]

Codecov Report

Merging #7062 (c881d23) into master (a7f1324) will decrease coverage by 0.59%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #7062      +/-   ##
==========================================
- Coverage   60.66%   60.07%   -0.60%     
==========================================
  Files          86       86              
  Lines        2705     2705              
  Branches      678      678              
==========================================
- Hits         1641     1625      -16     
- Misses        815      830      +15     
- Partials      249      250       +1     

Impacted Files	Coverage Δ
packages/core/src/api/client.ts	66.66% <ø> (ø)
packages/core/src/api/plugins.ts	33.33% <ø> (ø)
packages/core/src/api/window-events.ts	18.75% <ø> (ø)
packages/core/src/commands/context.ts	40.00% <ø> (ø)
packages/core/src/commands/resolution.ts	100.00% <ø> (ø)
packages/core/src/commands/tree.ts	76.00% <ø> (ø)
packages/core/src/commands/typeahead.ts	27.27% <ø> (-48.49%)	⬇️
packages/core/src/core/capabilities.ts	66.00% <ø> (ø)
packages/core/src/core/command-tree.ts	65.62% <ø> (ø)
packages/core/src/core/events.ts	76.66% <ø> (ø)
... and 77 more

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