Generate JS bindings from OpenAPI spec

SOLR-16346 added support to Solr's build to generate an "OpenAPI spec" file describing our v2 API.

Spec files can be used for a variety of purposes, including to generate client bindings in a variety of languages. We're already doing this in Java for creating v2 SolrRequest implementations, and Python generation is underway in SOLR-16835.

We would also benefit from generating clients for some of the other (i.e. non-Java) languages in Solr's codebase. The Admin UI uses Javascript/angular, the operator uses golang, etc.

This ticket covers generating a Javascript client that can be used in our Admin UI.