Add Integration Tests, Dev Environment & Switch to kr8s

[BonySmoke]

What does this change resolve?

• Add integration tests for all scenarios from the examples folder, as well as failed cases. They don't cover absolutely everything, but serve as a good base for reliability
  • Also update some examples for compatibility with the latest versions of NetBox, as well as for easier lookups in the tests
• Add a Makefile command to prepare a development environment
  • Create a Kind cluster
  • Deploy NetBox (unfortunately, I couldn't proceed with NetBox 4.5.0+ because it introduces API tokens v2 that are not yet well supported by the NetBox helm chart)
  • Build the operator image and deploy the operator chart with it
• Switch from pykube to kr8s as it looks more feature-rich and natural to use, e.g., it can apply YAML from files, which was essential for writing integration tests
• Upgrade all packages to the latest versions
• Update documentation

[github-actions]

Coverage report

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File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
app
kubernetes.py
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