[turbopack] Rename ClientReferenceSet (#81942)
# Rename ClientReferencesSet to ClientReferenceManifest for better clarity
## What?
Currently the `ClientReferenceSet` struct tracks information that allows us to efficiently create a manifest of css and js files referenced by entry points and server components.
Naming this is tough because we are really just doing half of an algorithm and the structures are dictated by the other half.
