Add e2e tests for Quick Draft section in Dashboard

[isabel_brison]

Splitting off a task from #52895.

Trac ticket: https://core.trac.wordpress.org/ticket/52905

Adds some tests for Quick Draft section in Dashboard.

I named the file "Dashboard" because we might think of other things to test on that page, and it seems right to separate tests by admin pages as they mostly have distinct types of functionality.

[johnbillion]

The first two tests here (for creating drafts) look solid and I think they should go in. The third test seems too fragile to me as it relies heavily on four consecutive page reloads happening within 500ms, and the value of that test is much lower.

I'd be in favour of committing the first two as they add value, but leaving the third test out to avoid a low value and fragile test.

[isabel_brison]

Thanks for the review @johnbillion ! Any action needed on my side?

[desrosj]

This was fixed in [51128].

Closing as this was committed in https://core.trac.wordpress.org/changeset/51128