kvserver: make all cluster settings system only

#98347 covers updating distribution cluster settings in the `kvserver` pkg to be `SystemOnly`. This issue tracks changing any other cluster settings in the `kvserver` pkg to be `SystemOnly`.

The remaining cluster settings are depended on by tests using a non-system tenant to modify the setting. Updating these settings from `TenantWritable` or `TenantReadOnly`, to `SystemOnly` will require updating fixing tests.

Complete list

```
kv.rangefeed.enabled
kv.closed_timestamp.target_duration
kv.closed_timestamp.side_transport_interval
kv.raft.command.max_size
kv.protectedts.reconciliation.interval
kv.protectedts.poll_interval
kv.protectedts.max_bytes
kv.gc_ttl.strict_enforcement.enabled
server.time_until_store_dead
```

The most depended (of tests using a non-system tenant) are `kv.rangefeed.enabled` or `kv.closed_timestamp.target_duration`.

Jira issue: CRDB-25464