During perf testing for bulkWrite we discovered that when we only allow a single document for an insert op we spend a large amount of time in IDL parsing since we need to parse 1000x BulkWriteInsertOp instead of allowing one BulkWriteInsertOp with 1000x documents. We saw significant performance speedups (+13%) when we use this form of parsing so we want to switch to using it permanently

This is an example commit of a prototype of this functionality. It works for the normal insert codepath but is not cleaned up and has not been tested with retryable writes, timeseries, fle, mongos, etc

This change should be mostly surgical, but there is one check we do that will be difficult with this new format and we will need to revisit.