Similar to NODE-4904 we have a few usages of our public CRUD API internally that use callbacks, we would have to jump through numerous "ts-ignore" hoops to get that code happy with the callback overload removals. 

AC

• Refactor internal callback usage in:
  • src/cursor/abstract_cursor.ts - executeOperation
  • src/encrypter.ts - MongoClient.close
  • src/operations/bulk_write.ts - bulk.execute
  • src/operations/collections.ts - listCollections().toArray()
  • src/operations/common_functions.ts - listIndexes().toArray()
  • src/operations/indexes.ts - listIndexes().toArray()
  • src/operations/is_capped.ts - listCollections().toArray()
  • src/operations/options_operation.ts - listCollections().toArray()