Overflow list: add option to keep children mounted

[KochiyaOcean]

Environment

• Package version(s): 3.7.0

Feature request

Current overflow list removes children from DOM when its invisible, and they will be loaded again if they be visible again.

Sometimes the operation of remove and create elements costs too much performance and affects other components, like css animation.

If there is an option that allows keep children in the DOM tree (e.g. just set display: none to them), overflow list will have better performance.

[giladgray]

@KochiyaOcean interesting idea, definitely see the use case and the precedent in other components. happy to review a PR!