Fixes test flakiness on OS X Safari and Android when using jQuery 3.
Fixes #20182 more
Refs #20191

Instead of doing a new assert.async(), just do a single one for the entire test
and let the .then() be async as well.

Closes #20190

Closes #19906

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* Use $.one() instead of $.on() since there are no $.off()s in the code.
* Remove unnecessary namespacing of listeners for the `scroll` & `load` events.
    These are vanilla DOM events (not custom jQuery namespaced events)
    and we're not using jQuery namespacing to manage these event listeners either (e.g. `$.off()`).

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Fixes #19878

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When a DOM node is passed to an HTML tooltip, the `title` node is only
moved if it is not already in the tooltip. Otherwise, `empty()` is used
instead of `detach()` before appending the `title` to avoid memory
leaks. If a DOM node is passed to a plain text tooltip, its text is
copied via jQuery `.text()`.

Replaces `.detach()` with `.empty()`, as `.detach()` is almost never
useful but instead leaks memory. The difference between `empty` and
`detach` is that the latter keeps all the attached jQuery events/data.
However, since we do not return the previous children, the user would
have to keep these themselves, thus they can `detach()` if necessary.

This is a port of https://github.com/twbs/bootstrap/pull/14552 to v4.

Fixes #16828
Closes #16865

as role="menu" is a very specific (and strict) ARIA pattern for
desktop-like application menus, and our dropdowns are often used
as pure navigation dropdowns, this change abandons ARIA menus for
a more open-ended and light-weight approach
(see http://heydonworks.com/practical_aria_examples/#submenus and
http://www.w3.org/WAI/tutorials/menus/flyout/#improve-screen-reader-support-using-wai-aria)
note that in dropdown.js, switched to now target ``.dropdown-menu``
instead of ``role["menu"]`` - this also prevents bootstrap scripts
from "bleeding" into non-bootstrap components on the same page.
also removed the ``role=["listbox"]`` part, which appears to be
vestigial/unused (only place in bootstrap that uses that
role are carousels, and their key handling is done separately)

add modal my gawd

Overall logic for this test appears broken, possibly relating to an
older version of Bootstrap that did not require explicit
`data-toggle="button"` on single toggle buttons?

Fixes issue #16008

Otherwise, the test doesn't properly fail when the fix is reverted.

Closes #16142 by merging it.

Closes #16219.

Closes #16151 by merging a rebased version of it that adds docs and 1 more assertion.