Currently MEF is looking through all assemblies and types every time for script packs and exports. This is potentially very expensive and will slow down progressively based on the number of types and assemblies.

This change will record the exact assemblies and types that have MEF exports when the cache is built. When loading in the fast path, it will specifically just load those assemblies/types directly into the MEF catalog (using TypeCatalog).

This will get completed after the initial manifest for assemblies is added.