feat(bigquery): Implement truncate with views

[iambriccardo]

This PR implements truncation in BigQuery in the following way:

• Tables are created with monotonically increasing names in the form table_name_[n].
• A view is created with the name table_name.
• Every time there is a new truncate in the events batch, the truncate will create a new table with sequence number n + 1 and will atomically move the view to the new table.
• In case of subsequent truncates on the same table, we will avoid creating empty tables, even though this case should be rare in practice.