Rewrite `retrieve_tests_metadata` and `update_tests_metadata` from Shell to Ruby

What does this MR do and why?

This merge request does several things:

• Rewrite retrieve_tests_metadata and update_tests_metadata from Shell to Ruby because:
  • Ruby is less error-prone than Shell
  • It's much easier to write Ruby tests than Shell tests
  • We also download files in parallel rather than in sequential
• Speed up job retrieve-tests-metadata with .fast-no-clone-job
• We add verify-tests-metadata which runs after update-tests-metadata to ensure we're not breaking the metadata
• Tests are added for scripts written in Ruby

Related to #473415

MR acceptance checklist

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