Dependencies: Rework OverlaySheet with the list of dependencies

• Port the whole thing to pragma ComponentBehavior: Bound, meaning no magical injected contexts are allowed in delegates;
• Create an overlay sheet on demand, reducing startup cost and time;
• Give an overlay sheet focus: there is not much to interact with via keyboard, but at least the focus isn't left behind, and it fixes the Escape key to close the sheet;
• Set implicit height to the estimated contentHeight, but do it in a smart way which doesn't cause back-and-forth loops when the ListView changes estimations as user scrolls away from a differently-sized section delegate;
• Drop QML import versions, add import aliases;

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Before:

After:

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Example of a glitched ListView when implicitHeight: contentHeight is left bound directly without this workaround:

Discover_-_ListView_vs_itself