Allow dropping cache for Protobuf format with SYSTEM DROP SCHEMA FORMAT CACHE

Why it matters

This feature enables users to explicitly clear or reset the cached schema information for the Protobuf format. It helps resolve issues caused by stale or outdated schema cache, ensuring that the latest Protobuf schema changes are applied without restarting the server.

How to use it

To drop the Protobuf schema cache, execute the following command in ClickHouse:

SYSTEM DROP SCHEMA FORMAT CACHE FOR Protobuf

This will clear the cached schema data for the Protobuf format, forcing ClickHouse to reload the schema on subsequent operations.