Add Real-World DAG Debugging Strategies to Airflow Docs

### Description

Right now, most of the documentation around debugging Airflow DAGs references `dag.test()` and the command line. While this is a viable way to debug DAGs, it's not typically the way that it is done at the enterprise-level.

Update this docs page to include more "practical" or E2E testing techniques for DAGs. This might include running a Task and inspecting its XComs. Or re-running a single Task via the UI to validate that it ran successfully. There are tons of ways that this is done!

Existing Docs: https://airflow.apache.org/docs/apache-airflow/stable/core-concepts/debug.html

### 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)

Start with the existing debug documentation page at https://airflow.apache.org/docs/apache-airflow/stable/core-concepts/debug.html and review its dag.test() and command-line guidance. Research practical enterprise DAG debugging approaches such as inspecting XComs and re-running a task from the UI, then update the page with useful E2E techniques and verify the documentation builds correctly.

Written by the indexing model from the issue text.