keyspace: make TSO keyspace group auto split configurable

## Enhancement Task

TSO keyspace group auto split currently uses hard-coded defaults:

- keyspace count split threshold: 40000
- auto-split patrol interval: 15m

Operators need a way to disable this behavior, or tune the threshold and patrol interval, without changing code.

### Task

Add keyspace configuration for TSO keyspace group auto split:

- `enable-tso-keyspace-group-auto-split`: enable or disable auto split.
- `tso-keyspace-group-auto-split-threshold`: configure the keyspace count split threshold.
- `tso-keyspace-group-auto-split-patrol-interval`: configure the patrol interval.

### Expected behavior

- Default behavior remains unchanged: auto split is enabled with threshold `40000` and patrol interval `15m`.
- Runtime keyspace config updates are applied to the keyspace group manager.
- When auto split is disabled, the patrol loop should skip automatic keyspace group split.

Locate the TSO keyspace group auto-split defaults, the keyspace configuration update path, and the keyspace group manager's patrol loop. Verify that the existing defaults remain unchanged, runtime updates reach the manager, and disabling the setting prevents automatic splitting.

Written by the indexing model from the issue text.