Create options list view for macOS

[borisovodov]

On iOS, iPadOS and visionOS OutlineGroup inside Form work right from the box.

Form {
    OutlineGroup(self.data, id: self.dataID, children: self.children) { dataElement in
        self.outlineGroupRow(dataElement)
    }
}

Therefore, it's necessary to create an analogue of this view on macOS.

To be

• [x] Add labeled content button
• [x] Add indentations on different level of hierarchy
• [x] Fix vertical padding between rows
• [x] Display OutlineGroup inside popover
• [x] Add white background as in List
• [ ] Create popover without arrow
• [ ] Set popover the same width as labeled content button

[borisovodov]

There is no way to use default AppKit NSPopUpButton, because item of this button is string only: https://serialcoder.dev/text-tutorials/macos-tutorials/popup-and-pull-down-buttons-in-appkit/