Resolve "Reconcile project templates with Auto DevOps"

What does this MR do?

Updates project templates to be compatible with Auto DevOps

• Update Rails template
• Update Spring template
• Update Express template
• Update template descriptions
• Flatten repositories
• Vendor files

Are there points in the code the reviewer needs to double check?

Projects should work as expected with Auto DevOps once imported.

Why was this MR needed?

Auto DevOps should be supported by project templates instead of using custom .gitlab-ci.yml files.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Closes #36762 (closed)