Update UITypeEditors to use modern FolderBrowserDialog instead of XP version

During review of PR #2305 it was [noted](https://github.com/dotnet/winforms/pull/2305#issuecomment-551158274)

> We should file a follow up issue that changes the folder picker to the newer one that Oren enabled way back when we first went open source.

The default folder dialog is from pre-Vista era, you have to opt-in to the modern version, which the code does not do (and there is no way for the user to override it either). Since the modern dialog will always be available under the supported operating systems it makes sense to always use it.