Incorrect format processing in VideoOutput with "basic" render loop

I met an issue when attempting to play video with the VideoOutput component using the ABGR8888 format. Occasionally, the video is processed as ARGB8888 instead of ABGR8888.

Steps to Reproduce:

1. Use VideoOutput to play a video in ABGR8888 format.
2. Set the render loop to "basic".
3. The issue occurs when QSGGuiThreadRenderLoop::ensureRhi() is called after last QQuickVideoOutput::initRhiForSink.

In this case, in QQuickVideoOutput, its window is set but the window's rhi is still empty. QQuickVideoOutput::initRhiForSink should be called when m_window->d->rhi is set too.

Workaround: Retrying with a timer solves the issue as the patch attached.

Ideally it should be updated right after rhi is set