Allow specifying instance type when submitting Vertex AI batch prediction job

[jamin-chen]

My batch prediction jobs are failing with an INTERNAL error. I had a video call with Google support and they told me it's due to the instance running low on RAM.

We should be able to specify the instance type when creating a Vertex AI batch prediction job:

python-aiplatform/vertexai/batch_prediction/_batch_prediction.py

Lines 209 to 215 in e0ba9c3

	aiplatform_job = jobs.BatchPredictionJob.submit(
	model_name=model_name,
	gcs_source=gcs_source,
	bigquery_source=bigquery_source,
	gcs_destination_prefix=gcs_destination_prefix,
	bigquery_destination_prefix=bigquery_destination_prefix,
	)