WIP: Remove the QA framework files and require them from the gitlab-qa gem instead

What does this MR do?

This removes the QA framework files and require them from the gitlab-qa gem instead.

This also move the QA scenarios from qa/qa/specs/features to qa/scenarios.

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

This depends on gitlab-qa which isn't released yet since gitlab-qa!136 (closed) needs to be merged first. Keeping the [WIP] prefix to ensure it's not merged before gitlab-qa!136 (closed).

Why was this MR needed?

To reduce the complexity and duplication of GitLab QA-related files/structure.

Does this MR meet the acceptance criteria?

• Documentation created/updated
• Tests added for this feature/bug
• Conform by the code review guidelines
  • Has been reviewed by a Backend maintainer
• Conform by the merge request performance guides
• Conform by the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Related to gitlab-qa#250 (closed) and gitlab-qa#94 (closed).