Some ALTER USER Queries Were Accepted - Fixes #71227 and #71286

Why it matters

This fix addresses an issue where ALTER USER queries that had no meaningful effect were still accepted. It improves input validation and ensures that only valid and purposeful user modifications are processed, preventing unnecessary or accidental operations.

How to use it

No special action is required from users. The fix is applied automatically in the ClickHouse update, preventing acceptance of meaningless ALTER USER queries.