This fixes the flaky test in "ViewLayoutCollapse.ts": "fix: should not dispose the instance when drag is cancelled".
The 'mouseenter' event wasn't consistently triggering properly on the drop target (LayoutEditor.ts - line 342) when the mouse was moved onto it.
The change simulates a "drag" over the drop target, moving the mouse into multiple positions over it, seemingly fixing the problem.
e00c7f7d2b