Tooltip: click focusable node then mouse away, tooltip remains

[bill]

For keyboard users, tooltips need to appear on focus and disappear on blur. However, when a node is focused by a mouse click, and a tooltip appears, it may obscure other things on the page.

For example, clicking an <input> makes a tooltip appear, covering up the form submit button.

In this case, the tooltip should disappear when the node is unhovered.

See #3811 for original work on tooltip/keyboard support.

[bill]

patch that ignores focus events when they come from a mouse click

[bill]

(In [25493]) Remove code to keep a tooltip open if the associated element still has focus (even though the mouse moved away). Code was added in [10444] but it's unclear why it's needed. I suppose it's for when a user tabs into a field and then accidentally moves the mouse over it, but that doesn't seem important enough to worry about. Fixes #13225, refs #3811 !strict.