[SIP-180] Implement a "Cost Estimation" Pre-Query Check

Since Superset enables users to run SQL queries directly against large-scale data warehouses like Google BigQuery, Snowflake, and Amazon Redshift. A significant risk in this environment is that a user, particularly one less familiar with SQL optimization, could inadvertently write a query that scans terabytes of data, incurring substantial and unexpected financial costs. Superset currently lacks a built-in "guardrail" to prevent this.

**Proposed Solution:** This feature would integrate Superset with the "dry run" or query cost estimation APIs that are provided by most major cloud data warehouses. Before executing a query from the SQL Lab or a dashboard, Superset would first send the query to the warehouse's estimation endpoint. If the estimated data to be scanned or the computed cost exceeds a user-configurable threshold, Superset would present a clear warning to the user, such as: "This query will process an estimated 5TB of data. Are you sure you wish to continue?".

**Impact:** This contribution would add a critical layer of financial governance and safety to Superset, making it a more robust and trustworthy tool for enterprise environments. It would prevent costly mistakes, encourage more efficient query writing, and provide administrators with greater control over resource usage.