Allow MaterializedView with Subqueries on Kafka Tables

Why it matters

Enables more flexible data transformations and processing by supporting subqueries in MaterializedView definitions that read from Kafka tables. This extends the capability of MaterializedView to handle complex queries on streaming data sources, improving data ingestion workflows.

How to use it

Define a MaterializedView using a SELECT statement that includes subqueries over Kafka tables as its source. No additional configuration is required beyond the usual MaterializedView and Kafka table setup.