Use correct RUBY_VERSION in all e2e child pipelines and improve pipeline code

What does this MR do and why?

Decouple gitlab project pipelines from base.gitlab-ci.yml file defined in pipeline-common project. This primarily fixes issue where wrong RUBY_VERSION has been used throughout all pipelines running in gitlab project due to base file defining it's own ruby version.

• Fixes using incorrect ruby version
• Fixes issue with omnibus cache version mismatch with ruby version
• Removes inclusion of irrelevant setup scripts from pipeline-common which are mainly used by live environment pipelines and not mr pipelines
• Refactors and removes some of the duplication in yml files
• Updates default artifact paths to suite cng and gdk tests instead of omnibus tests

Closes: Remove pipeline-common pipeline template inclus... (gitlab-org/quality/analytics/team#39 - closed)

MR acceptance checklist

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Additional validation

Externally added omnibus tests from gitlab-omnibus repo ensuring backwards compatibility is maintained: https://gitlab.com/gitlab-org/omnibus-gitlab/-/pipelines/1703040838