Add unit tests for CSPO controllers

[michal-gubricky]

/kind feature

Description: We propose the introduction of unit tests for CSPO controllers using the envtest package provided by controller-runtime for our Kubernetes operator.. This testing environment should facilitate the simulation of a real Kubernetes API server and enable comprehensive and realistic tests for our controller's behavior.

Acceptance Criteria:

• [ ] Add unit tests in the Go code
• [ ] The test setup is encapsulated and does not need external dependencies.
• [ ] Have Make target to run the tests easily.
• [ ] Run the tests in the CI with GitHub Action.