Airflow API for 'airflow dags reserialize'

### Description

An Airflow API endpoint to programatically reserialize dags, aligned with the `airflow dags reserialize `CLI command:
https://airflow.apache.org/docs/apache-airflow/stable/cli-and-env-variables-ref.html#reserialize

### Use case/motivation

Currently, I must exec into my Airflow webserver in order to run the CLI command to refresh dags.

However, I already have an Airflow client programatically communicating to the Airflow webserver API. It would be great to be able to request the API to refresh dags when required.

As a temporary solution, I have set a low interval of 1s for:
- min_serialized_dag_update_interval
- min_serialized_dag_fetch_interval

But have found high constant resource usage as a result to the Airflow services.

### Related issues

An extension of https://github.com/apache/airflow/issues/19432

### 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 documented `airflow dags reserialize` CLI command and the related issue #19432 to understand the existing behavior. Identify the Airflow webserver API entry point that should expose the same DAG reserialization operation. Done means clients can request a refresh through the API without exec access and the behavior matches the CLI command.

Written by the indexing model from the issue text.