As seen: https://github.com/ppy/osu/pull/17252/checks?check_run_id=5545717506
The `PlaylistsResultsScreen` takes a lease on the `Beatmap` bindable
when entered. During `SetUp`, the `Beatmap` bindable is reassigned but
fails in cases where an existing test instance of the screen hasn't been
exited yet. This fix moves the assignment into the `SetUpSteps` function
after `base.SetUpSteps` is called which will exit the existing screens
first.
The equality of samples is generally used to compare the sample
equality, not its full properties. For instance, we don't compare
`Volume` in the base implementation.
Having `IsLayered` here breaks actual usages of equality, ie. for
pooling purposes.