feat: add `pre_get_sources_script` for GitLab Runner 17+

[kayman-mk]

Description

Adds the pre_get_sources_script (GitLab Runner 17+) parameter which is filled with the value of pre_clone_script (GitLab Runner < 17).

The parameter was renamed. Deprecation warnings are shown in the logs of GitLab Runner 16. GitLab Runner 17 simply ignores the parameter and therefor the whole script. This might result in failing pipelines.

Verification

• [x] use Runner 16 and verify that the script is taken into account
• [x] use Runner 17 and verify that the script is taken into account
• [x] no errors and warnings are shown in the log

[github-actions[bot]]

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🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ COPYPASTE	jscpd	yes		no	1.64s
✅ REPOSITORY	checkov	yes		no	13.87s
✅ REPOSITORY	dustilock	yes		no	0.25s
✅ REPOSITORY	gitleaks	yes		no	1.52s
✅ REPOSITORY	git_diff	yes		no	0.01s
✅ REPOSITORY	grype	yes		no	13.16s
✅ REPOSITORY	secretlint	yes		no	0.96s
✅ REPOSITORY	syft	yes		no	0.34s
✅ REPOSITORY	trivy-sbom	yes		no	1.55s
✅ REPOSITORY	trufflehog	yes		no	5.38s

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

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