[server] Support table-level minimum in-sync replicas config

### Search before asking

- [x] I searched in the [issues](https://github.com/apache/fluss/issues) and found nothing similar.

### Motivation

Add a table-level minimum ISR option that overrides `log.replica.min-in-sync-replicas-number`, because replication factor is already configurable per table and different tables may require different durability and availability policies.

### Solution

_No response_

### Anything else?

_No response_

### Willingness to contribute

- [x] I'm willing to submit a PR!

Start by tracing the existing `log.replica.min-in-sync-replicas-number` configuration and how table-level replication settings are defined and applied. Determine the affected configuration, table metadata, and replication paths before deciding the scope; done should include a table-level minimum ISR that overrides the global setting while preserving the current fallback behavior.

Written by the indexing model from the issue text.