GraphQL: Add a provenance backend

Add a provenance backend and support the following fields

Content: firstReference allReferences(first: n)

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Migrated from T4430 (view on Phabricator)

assigned to @jayeshv

marked this issue as related to #4083

added GraphQL API priority:Low labels

changed the description

added activity::Implementation label

changed milestone to %GraphQL API

removed priority:Low label

added priority:Wishlist label

changed time estimate to 2d