Fetch endpoints.json dynamically instead of storing in repo

**Describe the solution you'd like**

The codebase should not contain endpoints.json. It should pull it down as part of the `npm install` step, so that the toolkit builds always embed/contain the most recent version.

Start by locating endpoints.json and the npm install/build entry points that package the toolkit. Trace how the file is currently included, then determine where the download should occur so builds contain the latest version. Done means endpoints.json is no longer stored in the repository and npm install produces builds with the fetched data.

Written by the indexing model from the issue text.