Tasks that are running when a DAG run reaches its timeout should optionally support `on_killed`

### Description The current functionality for task instances that are in the running state when a DAG run reaches its timeout is controversial (see #30264). It'd be great if users could optionally allow tasks' `on_kill` method to be called at this time. ### Use case/motivation Some users would like for externally running workloads (e.g. snowflake, emr, bigquery, etc etc) to stop executing when a DAG run times out. ### Related issues #30264 ### 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)