E2E to add new directory in Web IDE

Description of the test

Adds a new E2E to test adding a new directory in Web IDE. See first part of #270083 (closed)

Also adds missing testcase links for a different test.

Check-list

• Confirm the test has a testcase: tag linking to an existing test case in the test case project. NB the links will be added in a follow up MR once the testcase issues are created automatically.
• Note if the test is intended to run in specific scenarios. If a scenario is new, add a link to the MR that adds the new scenario.
• Follow the end-to-end tests style guide and best practices.
• Use the appropriate RSpec metadata tag(s).
• Ensure that a created resource is removed after test execution.
• Ensure that no transient bugs are hidden accidentally due to the usage of waits and reloads.
• Verify the tags to ensure it runs on the desired test environments.
• If this MR has a dependency on another MR, such as a GitLab QA MR, specify the order in which the MRs should be merged.
• (If applicable) Create a follow-up issue to document the special setup necessary to run the test: ISSUE_LINK