fix(bigquery-jdbc): maxResults was not honored for child jobs - #14973

Summary

Multi-statement SCRIPT queries failed to activate the BigQuery Storage Read API (HTAPI / Arrow) on child SELECT jobs even when EnableHighThroughputAPI=1 and result sizes exceeded the Read API activation thresholds.

Root Cause

• For standalone SELECT queries, BigQueryStatement.executeJob(...) fetches initial results via job.getQueryResults(QueryResultsOption.pageSize(querySettings.getMaxResultPerPage())) (default MaxResults=10000).
• QueryJobConfiguration.Builder.setMaxResults(...) on a SCRIPT query only applies to the parent coordinator job, not to the child jobs spawned by BigQuery.
• Both SCRIPT child-job result paths — BigQueryStatement.handleQueryResult(...) (case SCRIPT:) and BigQueryStatement.getMoreResultsImpl(...) — called currentJob.getQueryResults() with no options. Without a pageSize option, tabledata.list fetches up to 10 MB of rows in the first REST page, either fitting the entire result into page 1 (!results.hasNextPage()) or inflating rowsInPage so meetsReadRatio(...) evaluates to false and silently falls back to BigQueryJsonResultSet.

Fix

• Added a BigQueryStatement.handleQueryResult(String query, Job job) overload that resolves StatementType and SqlType from job, fetches results with QueryResultsOption.pageSize(querySettings.getMaxResultPerPage()), and delegates to handleQueryResult(query, results, sqlType, job).
• Updated both case SCRIPT: in handleQueryResult and getMoreResultsImpl to delegate to handleQueryResult(query, currentJob), eliminating duplicated child-job handling logic.

Tests

• BigQueryStatementTest: added unit tests covering handleQueryResult(String, Job) directly as well as multi-statement SCRIPT execution across execute(...) and getMoreResults(), verifying QueryResultsOption.pageSize(maxResults) is applied to every child job and BigQueryArrowResultSet is activated for large SELECT child jobs while preserving DML update counts and BigQueryJsonResultSet for small SELECT child jobs.
• ITStatementTest: updated testScript to assert BigQueryArrowResultSet and row counts across all 3 script statements via getMoreResults().
• ITCallableStatementTest: added testCallableStatementScriptWithReadApi covering CALL + multi-SELECT script execution with Read API enabled.