Fix same-frame UI clicks

[treeform]

Fixes short clicks that arrive as press and release in the same UI frame.

• Add completed-click handling for click-style widgets
• Cover buttons, icons, radios, checkboxes, dropdowns, list boxes, and window controls
• Add a Basic Window regression test

Tested with:

• nim r -d:silkyTesting tests/test.nim

[treeform]

I think this is what was caused by a bad windy Mac interaction. Where the windy creates a zombie Mac window and so it behaves very oddly