WIP: Add a new test to create a snippet

What does this MR do?

This will make it possible to validate the creation of a private snippet with appropriate content.

What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/52698

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer

If I had more time, I would:

• Locally ensure that this test passes and be preemptive to fix the likely failures
• Validate that the test snippet content is valid
• Strictly validate that the test is private as against it being public etc.
• Correct my naming error in the test from "it 'user creates a private project'" to "it 'user creates a private snippet'"
• Confirm what difference it would make if or not I add :smoke command as seen in the existing codes
• Correct my last assertion which is checking from a success alert to just look out for the content on the page