R1:91abc0f02720

Stop indexing the chunk data objects for large Files stored in multiple chunks

Summary:
Ref T13164. See PHI766. Currently, when file data is stored in small chunks, we submit each chunk to the indexing engine.

However, chunks are never surfaced directly and can never be found via any search/query, so this work is pointless. Just skip it.

(It would be nice to do this a little more formally on `IndexableInterface` or similar as `isThisAnIndexableObject()`, but we'd have to add like a million empty "yes…