Admin > Config should show the source for each config

### Description

In Airflow 2, you can see for each Config if it was set as the default, from airflow.cfg, or by environment variable.

This should be brought back for Airflow 3. This information is also not available in the API response, so I also cannot view it through developer mode in my browser.

### Use case/motivation

Seeing the config's source is helpful when the config's value is unexpected and I need to troubleshoot the Airflow deployment.

### 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)

Start by tracing the Airflow 3 Admin > Config view and its API response, then compare how Airflow 2 exposed each configuration source. Done means the source for every configuration is available in the API response and shown in the Admin > Config view.

Written by the indexing model from the issue text.