[Code Embeddings] Add a "with eligible duo projects" filter to the Projects GraphQL query

Context

With ad-hoc indexing of Code Embeddings, we can't rely on the Projects GraphQL query's withCodeEmbeddingsIndexed filter (introduced in !195699 (merged)) to populate the projects in the /include <repository> command.

Instead, we should populate the /include <repository> with projects that are eligible for Code Embeddings. This translates to projects that have Duo enabled.

Proposal

In the GraphQL Projects query, add a new parameter for withDuoEnabled. This should apply for all projects that have Duo Core / Pro / or Enterprise through their root organizations AND have Duo features enabled.