kvserver: complete a no-op below-raft migration

In order to remove a few code leftovers and fixing a split race bug #152199, it would be good to force apply all historical proposals on all replicas.

For RSE, we want the invariant that evaluated proposals don't touch the raft state. However, it is still possible today that a split proposal contains a write to `RaftTruncatedState`.

- https://github.com/cockroachdb/cockroach/blob/ee0bb8fa3912df192238a61e6d0e471f14408b2c/pkg/kv/kvserver/replica_app_batch.go#L496-L498

- https://github.com/cockroachdb/cockroach/blob/ee0bb8fa3912df192238a61e6d0e471f14408b2c/pkg/kv/kvserver/store_split.go#L115-L116

- https://github.com/cockroachdb/cockroach/blob/ee0bb8fa3912df192238a61e6d0e471f14408b2c/pkg/kv/kvserver/kvserverpb/state.proto#L61-L64

Jira issue: CRDB-54091