create a new index for span_status, dag_version_id in task_instance table

### Description When the TI table is huge(~ 10M records), , `_end_spans_of_externally_ended_ops` method([Link](https://github.com/apache/airflow/blob/912ccace3532e3c05a46f6a1cf9457c0de41db6b/airflow-core/src/airflow/jobs/scheduler_job_runner.py#L1085C9-L1085C43)) takes very long to finish(in our case, about 75 seconds). This particular sqlalchemy query was taking too long: ``` tis_should_end: list[TaskInstance] = session.scalars( select(TaskInstance).where(TaskInstance.span_status == SpanStatus.SHOULD_END) ).all() ``` After adding the following index, performance improved significantly ``` create index idx_span_status on task_instance (id, span_status); ``` Along with above, creating an index on dag_version_id(`create index idx_dag_version_id on task_instance (dag_version_id);`) also helped to improve DAG Processor performance. ### Use case/motivation Improve scheduler and Dag Processor performance when TI table has lot of records ### Related issues _No response_ ### Are you willing to submit a PR? - [ ] Yes I am willing to submit a PR! ### Code of Conduct - [x] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)