[server] Fix alter cluster configs

[leekeiabstraction]

Improve mechanism around altering certain dynamic cluster-config keys, and adds an integration test covering the behavior.

[polyzos]

@leekeiabstraction just one nit:

authorize(ALTER, cluster) now runs after building serverConfigChanges, so AlterConfigOpType.from(...) parses request data before any authz runs . This means that an unauthorized caller can trigger a parse error pre-authz. Maybe move the parsing after the authz block (or keep the baseline authorization at the very top).

Otherwise LGTM, and we can merge once CI is green.

[loserwang1024]

@leekeiabstraction Hi Keith, I saw your PR: #4179. Are you currently using Fluss in production, and is this change intended to address a production safety concern? I’m asking because it may break compatibility with my existing production deployment, in which case I may need to roll back the change(#4196).

If you need this in production, maybe we could add a configuration flag in a follow-up to preserve backward compatibility later.