Behat: make triggering actions in the question bank less dependent on the specifics of the UI

MDL-66816 is, I hope, going to change the question bank UI for the better.

However, that is going to break quite a lot of Behat tests, not just in core, but in plugins.

Therefore, we need to replace the old specific Behat code:

When I click on "Duplicate" "link" in the "Test question to be copied" "table_row"

with something that can be maintained, like

When I "Duplicate" the "Test question to be copied" question in the question bank

Because this will Behat tests for plugins, and because a lot of question type plugin authors like to use one branch for all Moodle versions, then we need to backport the Behat fix, so I am doing it in a separate issue.