It's easy to overshoot the bottom of the tooltip when cursoring to a
button, such as opening the commit from a blame tooltip. Before this
change the tooltip would immediately disappear, and now it sticks around
for a bit.

Also:

* Shares the implementation with `elements/text.rs`. This will
particularly be handy when it makes use of hoverable tooltips.

* Improves the fix to #21657.

- Now the element will no longer think it has an active tooltip that it
registers with the window.

- It will instead display the next available tooltip, whereas I believe
before the next available tooltip would be suppressed.

* Fixes bug where `cx.refresh()` wasn't called when text tooltip is
hidden due to a mouse down event.

* Ports over fix in https://github.com/zed-industries/zed/pull/14832 to
`elements/text.rs`

Release Notes:

- The tooltip for inline git blame now waits a bit before disappearing
when the mouse leaves it.