non Portaled confirm() dialogs are unstyled.

[keithamus]

Description

In #3840 we're no longer using <Portal> to place the dialog, but doing so we realised that the <BaseStyles> provider is missing from the confirm() call.

Steps to reproduce

1. Remove <Portal> from <Dialog>.
2. Call confirm()
3. Observe unstyled <Dialog>

Version

v36.4.0

Browser

No response