### 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(!windows.has(p_window));
	WindowData &wd = windows[p_window];
	if (p_active) {
		ImmAssociateContext(wd.hWnd, wd.im_himc);
		window_set_ime_position(wd.im_position, p_window);
	} else {
		ImmAssociateContext(wd.hWnd, (HIMC)0);
	}
}
void DisplayServerWindows::window_set_ime_position(const Point2i &p_pos, WindowID p_window) {
	_THREAD_SAFE_METHOD_
	ERR_FAIL_COND(!windows.has(p_window));
	WindowData &wd = windows[p_window];
	wd.im_position = p_pos;
	HIMC himc = ImmGetContext(wd.hWnd);
	if (himc == (HIMC)0) {
		return;
	}
	COMPOSITIONFORM cps;
	cps.dwStyle = CFS_FORCE_POSITION;
	cps.ptCurrentPos.x = wd.im_position.x;
	cps.ptCurrentPos.y = wd.im_position.y;
	ImmSetCompositionWindow(himc, &cps);
	ImmReleaseContext(wd.hWnd, himc);
}
void DisplayServerWindows::cursor_set_shape(CursorShape p_shape) {