`insertMany` uses bulkWrite internally.  when a bulk write operation is constructed, we add each bulk write operation to "batches" and throw an error if the operation is not a document (specifically, checking if it's an array and throwing if it is).  because `insertMany` uses bulkWrite, if a user provided a nested array in side an array of documents when inserting, they receive a rather unhelpful error from bulk write:

const client = new MongoClient(process.env.MONGODB_URI!);

async function newFunction() {  
  await client.connect();
  await client
    .db('foo')
    .collection('bar')
    .insertMany([{ name: 'bailey' }, [{ name: 'bailey ' }]]);
}

newFunction();

// MongoInvalidArgumentError: Operation passed in cannot be an Array

It would be nice if we threw a more helpful error here instead, such as "MongoInvalidArgumentError: insertMany expects an array of documents, element <> was an array".

Acceptance Criteria:

• Detect invalid arguments in insertMany and throw a helpful error from insertMany if a non-document element is passed into insertMany