batches: Numerical IDs for executions
Created by: eseliger
Cleanup: Give executions "vanity" numerical IDs scoped to the batch change they belong to in order to have prettier execution URLs like /batch-change-name/executions/2.
Created by: eseliger
Cleanup: Give executions "vanity" numerical IDs scoped to the batch change they belong to in order to have prettier execution URLs like /batch-change-name/executions/2.