ToolbarView should handle items grouping correctly when invisible

[oleq]

📝 Provide detailed reproduction steps (if any)

1. The grouping should never happen if the toolbar is invisible. Because it always leads to all items groped and weird things when other features (like positioning algorithm) when they see the toolbar in such state

2. The grouping that was triggered by changing ToolbarView#maxWidth when toolbar is invisible should be queued so the next time the toolbar shows up (ResizeObserver kicks in automatically), the items are re-grouped. This is a problem when maxWidth increased because there's no pressure to ungroup the items when the toolbar showed up.

Related to #6449.

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