Optimize set(): avoid recreating popperInstance by comparing props

[atomiks]

cc @KubaJastrz not sure if this type can be better

This will compare the previous props with the new options being passed to set() - if none of them changed, there is no point recreating the popperInstance (which is somewhat expensive).

This is mainly for the React wrapper which has no diffing (to conserve bundle size) because the props will always be passed to set() on each render, leading to the popperInstance being recreated each time. In the vanilla lib usually they won't be doing this [I think]

[KubaJastrz]

Fixed types in 8864d9c.

About eslint rule: to comply with the "array" setting, I'd have to write (keyof Props)[] which I find less readable, but I can revert it if you want.

[atomiks]

Great, thanks!