Add support for cross index page moves

When moving a page from one namespace to another it might happen that the target is different. In such case the page should be explicitly removed from the original index. To do this we introduce a new field to UpdateEvent named movedFrom. During deduplication we take care of forwarding the original movedFrom field to the latest rev based event. We then introduce a new process function after the CirrusNamespaceIndexMap function to emit an extra delete event if the source index the page is moved from is different from the target index.

Bug: T331127