E2E: Stabilize and Refactor transfer_project_spec

What does this MR do and why?

This MR addresses a few issues with transfer_project_spec:

1. The namespace select dropdown initially opens downward and can trail off the screen if it is too close to the bottom. Then, sometimes while the test is searching, the dropdown corrects itself and opens upward. I think during this transition, the element is clicked in the dropdown but doesn't properly get selected. I've added a method to scroll to the transfer project section so that it is centered within the window.
2. click_element would not error out if the confirm_danger_button was disabled. I added a retry to wait for the button to be enabled first before proceeding.
3. Additional refactoring and cleanup

Recording of dropdown issue in the test:

transfer_project_spec_dropdown_issue

Resolves #375670 (closed)

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