Re-opening: In-flight DAG Import Errors Cause Tasks to Fail without Logs

### Apache Airflow version 2.5.1 ### What happened Today, if a DAG is running, and it has a top-level Variable.get() command, and that Variable is deleted while the DAG is still running, the DAG’s next task(s) will fail with no task logs (assuming the Variable eventually gets re-introduced), because the DAG cannot be parsed. I suspect this would happen with anything that can cause an import error, but I’m able to easily reproduce it using Variables. ### What you think should happen instead Once the DAG is able to be parsed/imported, any tasks that failed due to this problem should say something along the lines of "Task timed out due to a DAG import or parse error." ### How to reproduce 1. Create an Airflow Variable with the key "some_variable" 2. Trigger a DAG that makes a top-level call to Variable.get("some_variable"). While the DAG is running, delete the Airflow Variable. 3. Wait 10-15 minutes or so 4. Recreate an Airflow Variable with the key "some_variable" ### Operating System n/a ### Versions of Apache Airflow Providers _No response_ ### Deployment Astronomer ### Deployment details _No response_ ### Anything else Re-opening #29984 after discussion regarding improved logging capabilities making it possible to surface this information to DAG authors rather than administrators. ### Are you willing to submit 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)