Make QRhi::setQueueSubmitParams easily usable multiple times in a single frame

QRhi::setQueueSubmitParams() allows passing native GPU sync objects (e.g. VkSemaphore) to Qt when implementing native API rendering in QML. The passed sync objects are only used for the current frame.

Currently, setQueueSubmitParams() will replace any objects passed to a previous setQueueSubmitParams() call within the same frame.

This is an issue when a single QML window has multiple items with native API rendering, as each item may need to pass its own sync objects to Qt.

I believe setQueueSubmitParams() should really be addQueueSubmitParams() and it should not overwrite other sync objects passed to previous calls of it during the current frame.

If modifying and/or renaming this method is not possible, we should at least be able to query current sync objects with a queueSubmitParams() method or similar. This would allow QML items to query current sync objects, append its own sync objects to the list and then replace the old list with the new expanded one.