Add Nouveau indexes' info in our monitoring API

[m5r]

What feature do you want to improve?
With the upcoming implementation of CouchDB Nouveau, we need to monitor Nouveau indexes to get the data up on our observability dashboard

Describe the improvement you'd like
Use CouchDB's APIs to track any existing Nouveau indexes in API's monitoring service.

Additional context
GET /{db}/_design/{ddoc}/_nouveau_info/{index} docs

[m5r]

Merged to the couchdb-nouveau branch (related PR #9541), will be released alongside Nouveau