Move clear search test to JS to reduce overkill

What does this MR do?

Move clear search test from rspec to JS to reduce overkill. See https://gitlab.com/gitlab-org/gitlab-ce/issues/33661

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

The test is not totally equivalent. Previously it was a full end-to-end test whether the clear search button removes any filters and lists all issues. Now we just ensure it clears the value/query used to redirect the user to the new page.

Why was this MR needed?

Reduce rspec overkill to help reduce overall test time.

Does this MR meet the acceptance criteria?

• Tests added for this feature/bug
• Review
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

See https://gitlab.com/gitlab-org/gitlab-ce/issues/33661