workload: implicit scatter when splits is set

**Describe the problem**

When the `--splits` workload flag has a positive value, the workload will also scatter the split ranges.

https://github.com/cockroachdb/cockroach/blob/56cf7310d0ff3937f057859d44f2d217632c82f6/pkg/workload/workloadsql/workloadsql.go#L186-L187

This is unexpected, since some workload implementations also offer the ability to scatter when the `--scatter` flag is given in tpcc or kv.

**Expected behavior**

Remove `scatter` from `kv` and `tpcc`, or add the scatter option explicitly to other workloads and remove the implicit scatter mentioned above.

**Environment:**
- All versions

Jira issue: CRDB-33247