[ci skip]

(reported by ianhernandez in Slack)

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.

Related to #17314.

[ci skip]

[ci skip]

Use the `row` class on the `form-group`, and change the `control-label` class to `form-control-label`

And link to a relevant blog post w/ more info.
Refs #16966
[skip sauce]

Fixes grammatical erratum from cf7819d8

Fix #17234

Fix #17182

Otherwise the "Heads up!" is at the end of the previous line, making the connection to the warning unclear.