fix(log): add custom error handler for Kubernetes API errors

[ritwikranjan]

Description

This pull request includes changes to improve error handling and logging in the Kubernetes watcher and to simplify error checking in the endpoint reconciler. The most important changes include adding a custom error handler for the Kubernetes watcher, importing necessary packages, and simplifying error handling logic.

Improvements to error handling and logging:

• pkg/k8s/watcher_linux.go: Added a custom error handler retinaK8sErrorHandler to log specific Kubernetes API server errors and tag them for easier identification.
• pkg/k8s/watcher_linux.go: Registered the custom error handler in the init function to ensure it is used by the watcher.

Code simplification:

• pkg/controllers/operator/cilium-crds/endpoint/endpoint_controller.go: Simplified the error checking logic in handlePodUpsert by removing redundant error check.

Checklist

• 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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[ritwikranjan]

this change is unrelated but was quick so did it, we have already checked this condition before so it was an always true condition