Test that inserts and upserts respect null _id values

In the context of this ticket, "null" refers to the BSON null type (0x0A).

This should exercise insertOne, insertMany, updateOne, updateMany, replaceOne, and bulkWrite. Update commands will use the "upsert" option.

SPEC-1135 should ensure that drivers can report a null upserted ID in a result object. Since reporting of inserted IDs is optional, not all drivers will need to test for that. However, all drivers will be able to assert on expected collection data following the write operation.