Description

In several editors (Widgets, Navigation, Storybook playground) the block toolbar doesn't maintain position correctly when scrolling, it drifts up the page.

Step-by-step reproduction instructions

1. Add enough blocks in an editor to get a scrollbar
2. Select a block
3. Scroll

Expected behaviour

The block toolbar remains anchored to the block

Actual behaviour

The block toolbar doesn't remain anchored (it drifts off in the wrong direction).

This is hard to observe in the navigation editor, as the toolbar is pinned above the nav block, but it does happen (it can be more easily seen by adding extra padding in the page layout).