Consider adopting a positioning library for dropdown / related components

[ang-zeyu]

Frontend positioning is generally difficult and may be better left to well established libraries with more robust functionalities (e.g. dynamic flipping of floating elements). This may help reduce lower level concerns and allow us to extend the components' functionalities more easily.

e.g. https://floating-ui.com/ (formerly popperjs)

[kaixin-hc]

Related: #1429

[Tim-Siu]

This might also help with #572