Godot version: 307b1b3a5
OS/device including version: windows10
Issue description:
title bar is visible in dialog windows in Windows(os). also dragging them around makes the window lagging



We should probably hide the minimize/maximize buttons for modal dialogs like these. This would free up some space for the window title to display.
IMO, the Window's title bar and the border should be hidden, and we should draw the title and a close icon.
@ThakeeNathees Indeed, switching to client-side decorations is a long-term plan but it'll take a fair amount of effort.
Why not let some of these be inside the same window? It's not like new Node Dialog needs to be a new Window....
I think that small dialogs should also be not resizable. I've always found "unprofessional" that a dialog with very little content can be resized so it looks weird, as if the UI was unpolished.
I don't think this should be classified as a bug, and its a bit difficult to infer which dialogs should be resizable and which should not. This is not something that could be done automatically in the AcceptDialog base class, but something that someone has to go and disable in every dialog that they don't think should be resizable.
Most helpful comment
I think that small dialogs should also be not resizable. I've always found "unprofessional" that a dialog with very little content can be resized so it looks weird, as if the UI was unpolished.