Evaluate if and how we should change modals for window actions

[ggeisler]

We originally made all modals as effectively workspace modals (i.e. the scrim covers the entire workspace and prevents any other action in the workspace until the modal is cleared, rather than a window that only applies to the window where the action originated). However, some of these actions are actually window actions (e.g. download and share). In theory these should produce window-level modals. But window modals are more likely to run into space constraints so we need to look at all the cases and decide how to resolve the tradeoff.