### 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
EnumScreenData *data = (EnumScreenData *)dwData;
	if (data->monitor == hMonitor) {
		data->screen = data->count;
	}
	data->count++;
	return TRUE;
}
static BOOL CALLBACK _MonitorEnumProcCount(HMONITOR hMonitor, HDC hdcMonitor, LPRECT lprcMonitor, LPARAM dwData) {
	int *data = (int *)dwData;
	(*data)++;
	return TRUE;
}
int DisplayServerWindows::get_screen_count() const {
	_THREAD_SAFE_METHOD_
	int data = 0;
	EnumDisplayMonitors(nullptr, nullptr, _MonitorEnumProcCount, (LPARAM)&data);
	return data;
}
int DisplayServerWindows::get_primary_screen() const {
	EnumScreenData data = { 0, 0, 0 };
	EnumDisplayMonitors(nullptr, nullptr, _MonitorEnumProcPrim, (LPARAM)&data);
	return data.screen;
}
typedef struct {
	int count;
	int screen;
	Point2 pos;
} EnumPosData;
static BOOL CALLBACK _MonitorEnumProcPos(HMONITOR hMonitor, HDC hdcMonitor, LPRECT lprcMonitor, LPARAM dwData) {