Support ALTER TABLE for Memory Databases in ClickHouse

Why it matters

This feature enables users to modify the schema of Memory database tables in clickhouse-local using ALTER TABLE statements, improving flexibility and usability in local, in-memory data processing scenarios.

How to use it

Users can now apply standard ALTER TABLE commands on tables created in Memory databases while working in clickhouse-local. For example, after creating a table in a Memory database, use an ALTER TABLE statement to add, modify, or drop columns as needed.