Popups don't fit into screen

[KoBeWi]

Godot version:

011d201

OS/device including version:

Windows 10

Issue description:

nuff said

[EricEzaM]

Ugh.... a regression from #44906.

The size of the popup menu is not set. set_as_minsize() worked because it called set_size(get_contents_minimum_size());, so then the popup size would be set correctly before the adjust_popup_rect method was called. But now, this code is being called before it is drawn (and it's size is not set manually), so the size is unknown.

I have investigated further and the flow of logic is pretty weird...

1. PopupMenu::popup()
2. Window::popup()
3. In Window::popup(), calls Popup::_popup_adjust_rect(), which in this case does nothing because it still thinks the popup is tiny.
4. In Window::popup(), calls set_size(adjust.size)
5. set_size() calls _update_window_size, which enforces size limits.
6. Then finally the size limit is get_contents_minimum_size(), and the size is set to the maximum of the contents size, the min_size and the current size.
7. So this is weird because set_size is called with a size of [36, 12], but after that method returns, the size is then [310, 428] (or whatever the size should be)

This is a really weird way of doing it imo. To fix this, I just call _update_window_size() in Window::popup() before doing the _popup_adjust_rect(), so that the size is correctly calculated before adjusting.