### Godot version

4.0.beta12

### System information

Windows 11, RTX 3080

### Issue description

When a Window Node is created with it's Transparent flag set to true and Project Settings --> Display --> Window --> Subwindows --> Embed Subwindows is false, the Window has a black background. By cycling the transparent flag from false and back to true again, during runtime, the window's background then becomes transparent. 

### Steps to reproduce

Attempt to create a Non-embedded Subwindow with a transparent background using the appropriate flags. 

### Minimal reproduction project

Note: this project is from Reddit user [gongpha](https://www.reddit.com/user/gongpha/) and his Reddit post [Learning a Godot 4.0 Window node](https://www.reddit.com/r/godot/comments/xr8yxn/learning_a_godot_40_window_node/)

https://github.com/gongpha/godot4-window-test
_THREAD_SAFE_METHOD_
	ERR_FAIL_COND_V(!windows.has(p_window), Size2i());
	const WindowData &wd = windows[p_window];
	
	if (wd.minimized) {
		return Size2(wd.width, wd.height);
	}
	RECT r;
	if (GetClientRect(wd.hWnd, &r)) { 
		return Size2(r.right - r.left, r.bottom - r.top);
	}
	return Size2();
}
Size2i DisplayServerWindows::window_get_size_with_decorations(WindowID p_window) const {
	_THREAD_SAFE_METHOD_
	ERR_FAIL_COND_V(!windows.has(p_window), Size2i());
	const WindowData &wd = windows[p_window];
	RECT r;
	if (GetWindowRect(wd.hWnd, &r)) { 
		return Size2(r.right - r.left, r.bottom - r.top);
	}
	return Size2();
}
void DisplayServerWindows::_get_window_style(bool p_main_window, bool p_fullscreen, bool p_multiwindow_fs, bool p_borderless, bool p_resizable, bool p_maximized, bool p_no_activate_focus, DWORD &r_style, DWORD &r_style_ex) {