Autocomplete has lower z-index than ui-dialog

Tagging Field UX as upcoming Field UI improvements will likely increase the number of autocomplete inputs in dialogs.

Setting to NW, comments in MR.

This problem does not exists with the themes like Claro but this can only be reproduced with themes like Olivero.

I tested this with an autocomplete field in Views UI and at least there, it's working as expected in both Claro and Olivero. When I tested this, the autocomplete was rendered inside the dialog, meaning that it is in a different stacking context with the dialog. Because of that we shouldn't have to adjust the z-index against the modal.

Can someone who can reproduce the problem add the steps to the issue summary so that we can assess what's the root cause to the bug? I'm untagging this from the Field UX for now since the impact of this issue is hypothetical, and there are no steps to reproduce this.

Discussed with @bnjmnm and @Utkarsh_33 and they explained that reproducing this would require modifying appendTo option. I don't think we can provide a consistent behavior for this option because this option allows placing the tray in any stacking context. I think it's fine for us to expect that if someone wants to define the appendTo option, that they would also have to define an appropriate z-index for the tray, depending on where they are rendering the tray.