chore: Improves CI caching and efficiency

[sbaerlocher]

• Adds caching for test dependencies, Trivy database, Python dependencies, and MegaLinter to speed up CI runs.
• Updates Docker build caching to use registry cache in addition to GHA cache.
• Adds a matrix strategy to the performance test job to run different test types in parallel.
• Fixes issue with installing dependencies inside docker.
• Removes dependabot configuration file.

[github-actions]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Warnings	Elapsed time
✅ ACTION	actionlint	3		0	0	0.28s
✅ COPYPASTE	jscpd	yes		no	no	1.51s
✅ DOCKERFILE	hadolint	1		0	0	0.43s
✅ EDITORCONFIG	editorconfig-checker	4		0	0	0.31s
✅ REPOSITORY	checkov	yes		no	no	10.34s
✅ REPOSITORY	devskim	yes		no	no	0.94s
✅ REPOSITORY	dustilock	yes		no	no	0.86s
✅ REPOSITORY	gitleaks	yes		no	no	0.13s
✅ REPOSITORY	git_diff	yes		no	no	0.0s
✅ REPOSITORY	grype	yes		no	no	23.52s
✅ REPOSITORY	kics	yes		no	no	14.4s
✅ REPOSITORY	secretlint	yes		no	no	0.56s
✅ REPOSITORY	syft	yes		no	no	1.19s
✅ REPOSITORY	trivy	yes		no	no	5.04s
✅ REPOSITORY	trivy-sbom	yes		no	no	0.2s
✅ YAML	prettier	3	0	0	0	0.63s
✅ YAML	yamllint	3		0	0	0.36s

See detailed report in MegaLinter reports
Set VALIDATE_ALL_CODEBASE: true in mega-linter.yml to validate all sources, not only the diff