Deprecate LibraryDiscovery and use LibraryDiscoveryCollector instead

Problem/Motivation

This class uses a class property for static caching, but it's a very thin wrapper around the cache collector which also does static caching. Probably we had this before we added the cache collector.

We can make library.discovery just be the cache collector itself without the extra service/class, less indirection.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet