Enhance e2e (end-to-end) tests for MyDSpace page

[tdonohue]

Describe the bug

Enhance the existing e2e tests in my-dspace.cy.ts to include additional interactions that are possible on the MyDSpace page. These include:

• Searching all past submissions
• Drag & drop of a file to start a new submission
• Start a new Submission (of various types) using the "+" dropdown (to right of drag & drop box)
• Start a new Submission using the "import" dropdown (to the right of drag & drop box). We may need to consider "mocking" a response for one of the import tools in order to avoid actually hitting their API.
• Switch to "Workflow tasks" and verify that you can perform various workflow actions (e.g. Claim, Approve, Reject, Edit, Return to Pool, View).
• Switch to "Supervised Items" view and perform various actions on that page. (NOTE: This may require first creating a supervised item, as they don't seem to exist in our current demo data set.)

Expected behavior

The MyDSpace page and actions should be more fully tested

Related work

Subticket of #3978