hareware decoder + 0-copy rendering does not work on multiple windows/widgets

[wang-bin]

in qml rhi example.

• swdec + rendercallback update + multiwindows: last window is updated
• swdec + timer update + multiwindows: good
• hwdec + timer update + window(s): the last item of a window is updated
• hwdec + rendercallback update + window(s): the last item of the last window is updated
• VT + thread metal rhi loop + timer update + windows: last item of last window updated, some others may show and slow. unsafe
• VT + basic metal rhi loop + timer update + windows: last item of last window updated, some others may show but not fluent
• VT + GL+ timer update + windows: last item of last window updated, some others may show correctly

qtmultiwidgets is the same.