QA scenario to add/edit/delete a file via the Web UI

What does this MR do?

Adds tests for Add/Edit/Delete a file via the Web UI.

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

1. I had to add scope resolution operator (::) to File in qa/qa/page/view.rb since this PR introduces QA::Page::File page object module that was clashing with Ruby's File class. Other option was to rename the QA::Page::File module but I could not come up with a better name. I thought of FilePO (PO as in Page Object) but I did not like it.

2. I intentionally used #editor>textarea selector for editor textarea instead of .ace_text-input since the later is not there in the .haml file and therefore I could not add it to the view block for selector coupling/ view sanity testing (Test::Sanity::Selectors).

Why was this MR needed?

To improve test coverage and catch regressions around the file add, edit and delete functionality.

Does this MR meet the acceptance criteria?

• Tests added for this feature/bug
• Conform by the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• 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
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

#48464 (closed)