Long running index builds don't seem to update stats until complete

On the latest build (1844) I loaded 5M items into the default bucket before creating any index and then ran "create primary index on default using GSI".

I noticed in the UI that the statistics around index and disk size (among others) didn't update until quite a while into the initial build and then after the "items remaining" had reached 0, the disk and index sizes were still not correct.

In general, it's hard to tell what the indexer is doing and when it is considered "done" via the UI.

Let me know if screenshots and/or logs are most useful, this should be fairly straightforward to reproduce. We might need a bit of PM guidance in terms of what we want the behavior to be.