6.x branch fix 

Unknowns

• How do we know which ids were inserted or not if the error is not specific to an index? (Top-Level error), does that indicate all inserts failed?

Acceptance Criteria

Implementation Requirements

• Make BulkWriteResult.insertedIds reflect actual inserted docs in insertMany, even when no items are inserted / invalid objects are passed in

Testing Requirements

• Ensure user test passes for insertMany and bulkWrite
• When top level error (in resultHandler function) occurs for bulkWrite, handle insertedIds appropriately