Explicit statement types and new data skew metrics

The QueryResponse object now includes a statementType field, allowing developers to programmatically determine if a query was a SELECT, MERGE, CREATE_TABLE_AS_SELECT, or one of many other DDL/DML operations without manual parsing. Additionally, the SkewSource schema adds outputBytesMax, outputBytesMedian, and outputBytesP95. These metrics provide a granular look at partition output sizes within a query stage, making it significantly easier to identify and debug performance issues caused by uneven data distribution (skew).