[PLUGIN-1948] Fix ClassCastException in BigQuery source plugin for table definition

[adrikagupta]

When fetching table metadata, the plugin incorrectly assumes all BigQuery tables are standard tables and attempts to cast the TableDefinition directly to a StandardTableDefinition - link.

The pipeline crashes with the following error:

java.lang.ClassCastException: class com.google.cloud.bigquery.AutoValue_MaterializedViewDefinition cannot be cast to class com.google.cloud.bigquery.StandardTableDefinition

This PR fixes this issue.

Testing

• Created a pipeline with BQ source and added materializing view as the table. Successfully ran the preview and pipeline deployment.

Also tested the below to verify non materializing view (standard table) scenarios:

• Created a pipeline with BQ source and added range-partitioning table with & without required paritioning filter as true. Successfully ran the preview and pipeline deployment.
• Created a pipeline with BQ source and added ingestion partitioning table with required paritioning filter as true. Successfully ran the preview and pipeline deployment.

[vikasrathee-cs]

LGTM