Metadata format improvements

[Jand42]

Currently every JS-translated assembly content is encoded to a single binary resource which is deserialized in full for both compilation and sitelets runtime.

Multiple approaches for improving compiler and runtime performance is possible:

• Separate assembly contents info, expressions, and code dependency graph. Compilation should not need dependency graph of other assemblies, sitelets/rpc runtime should not need expressions, contents info used by both
• Deserialize expressions lazily (keep them as "pointers" to a byte array otherwise). Compiler need expressions for inline nodes only, packager+writer need expressions for non-inline nodes only. So a further split is possible
• Shrink code dependency graphs using strongly-connected component search. Shrink it further for sitelets runtime where only the resource nodes are relevant targets