chore(cli): refactor CLI to allow better testing interface + add tests

[alexcastilio]

Description

kubectl-retina CLI does not have e2e tests to validate its behavior. For that, some refactoring is needed.

This PR:

• refactors CLI code to allow injection of fake kubeclient for testing purposes. This allows the creation of tests that can validate that kubernetes resources are created as expected.
• Add some tests for capture create and capture delete commands to confirm that main arguments are behaving as expected.

Other tests will be added in the future and this code will be a reference for that.

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• I have read the contributing documentation.
• I signed and signed-off the commits (git commit -S -s ...). See this documentation on signing commits.
• I have correctly attributed the author(s) of the code.
• I have tested the changes locally.
• I have followed the project's style guidelines.
• I have updated the documentation, if necessary.
• I have added tests, if applicable.

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[SRodi]

Thanks for this @alexcastilio! I approve as I do not see any major issues with this PR, a few generic non-blocking comments:

• Documentation: Consider updating CLI documentation (help output, README, or developer docs) to reflect the new structure and testing approach.
• Extending Tests: Future PRs could extend testing to other CLI commands for full coverage.
• Minor: There are some places where debug output or error messages could be even more descriptive, but overall they are reasonable.