refactor: Moves the Explore form_data endpoint (#18151)

* refactor: Moves the Explore form_data endpoint

* Removes unused imports

* Fixes openapi schema error

* Fixes typo

* Renames and UPDATING.md

UPDATING.md

@@ -46,6 +46,7 @@ assists people when migrating to a new version.
 
 - [17589](https://github.com/apache/incubator-superset/pull/17589): It is now possible to limit access to users' recent activity data by setting the `ENABLE_BROAD_ACTIVITY_ACCESS` config flag to false, or customizing the `raise_for_user_activity_access` method in the security manager.
 - [17536](https://github.com/apache/superset/pull/17536): introduced a key-value endpoint to store dashboard filter state. This endpoint is backed by Flask-Caching and the default configuration assumes that the values will be stored in the file system. If you are already using another cache backend like Redis or Memchached, you'll probably want to change this setting in `superset_config.py`. The key is `FILTER_STATE_CACHE_CONFIG` and the available settings can be found in Flask-Caching [docs](https://flask-caching.readthedocs.io/en/latest/).
+- [17882](https://github.com/apache/superset/pull/17882): introduced a key-value endpoint to store Explore form data. This endpoint is backed by Flask-Caching and the default configuration assumes that the values will be stored in the file system. If you are already using another cache backend like Redis or Memchached, you'll probably want to change this setting in `superset_config.py`. The key is `EXPLORE_FORM_DATA_CACHE_CONFIG` and the available settings can be found in Flask-Caching [docs](https://flask-caching.readthedocs.io/en/latest/).
 
 ## 1.4.0