Cannot explicitly set zIndex for MenuList

[martinpengellyphillips]

🐛 Bug report

I need to explicitly set zIndex on MenuList to overcome an ordering issue in my application. Currently it seems that any passed zIndex has no effect as it is not passed to the wrapping popper element. This is similar to #2928 - however, in my case using Portal is not an option at present due to #3201.

In the below image, zIndex={4} was passed to MenuList.

💻 Link to reproduction

See prior https://codesandbox.io/s/elastic-jones-monv9

🧐 Expected behavior

zIndex is set on the corresponding popper element when passed as a prop to MenuList.

[segunadebayo]

Resolved in #3210, now available in the latest version

[kennycrosby]

@segunadebayo this is fixed if a user explicitly adds the zIndex as a prop to MenuList but adding the zIndex to baseStyle or to a variant does not work. Pointing out that this is also the case with the Tooltip bg, works as an explicitly set prop but NOT as a baseStyle or variant.