Content Hub Metadata Cache Route Not Defined

Problem/Motivation

When loading the H5P editor, the console shows a 404 error for one of the editor's AJAX callbacks. The route will look something like `/h5peditor/304a1e4b52689/186/content-hub-metadata-cache`, although the inner paths (token and content id) will vary.

Steps to reproduce

Open your browser's developer console.
Add a new node (or edit and existing one) that contains an H5P field and uses the H5P Editor field widget.
You will see a 404 error when the H5P editor tries to load the hub metadata cache file

Proposed resolution

The endpoint needs to be added to the h5peditor.routing.yml file and any additional code needs to be added / cleaned up.

Remaining tasks

The item above and also testing the feature that uses this data to see if it works

User interface changes

TBD

API changes

None

Data model changes

None