Toward #9580

pandas.dataframe.to_csv() by default exports data index as an column
with empty column name. This causes uploading the export csv file to
fail because AutoML Tables does not allow empty column names. Given
that the data index is not useful for training the model. This PR
fixes the problem by setting the index argument to false so that the
index is not exported.

…#9779)

Disable early stopping is turned off by default. It's defined in proto
here:
https://github.com/googleapis/google-cloud-python/blob/19ccb8527897caa9e4139a5c023a2e9b217a902b/automl/google/cloud/automl_v1beta1/proto/tables.proto#L196

This PR:
- exposes disable_early_stopping option for TablesClient.create_model.
- changes the default value of create_model's parameter model_metadata
  from empty dict to None. Default parameter values in Python is
  non-intuitive: http://effbot.org/zone/default-values.htm

…ction, text classification, text extraction; add `batch_predict`; add `deploy_model`, `undeploy_model`, `export_model`; add annotation specs (via synth) (#9628)