fix(chartvalidator): should not produce 'no kind' warning on empty manifests

[bosbaber]

This pull request primarily improves the robustness and test coverage of the image extraction logic in the Helm chart validator, especially for multi-document YAML files and real-world Kubernetes manifests. The most significant change is the addition of comprehensive tests to ensure correct image extraction from complex manifests, as well as a small enhancement to gracefully handle empty YAML documents. There are also some minor code cleanups.

Enhancements to image extraction robustness and test coverage:

• Added new tests in engine_image_extraction_test.go to verify correct image extraction from multi-document YAML files, real-world Helm chart outputs (such as the Traefik example), and manifests containing a mix of workload and non-workload resources. These tests ensure only relevant images are extracted and full registry paths are preserved.
• Updated extractImageFromManifest in engine_image_extraction.go to gracefully skip empty YAML documents, preventing errors when encountering comment-only or blank sections in multi-document files.

Minor code cleanup:

• Removed unused getJobCount function and associated import of runtime from utils.go. [1] [2]
• Removed extraneous blank lines in both engine_image_extraction.go and engine_image_extraction_test.go for code clarity. [1] [2] [3] [4] [5] [6] [7] [8] [9]

These changes collectively improve the reliability and maintainability of the image extraction engine, especially for real-world Kubernetes workloads.