Cross-partition shared sources now compile

A NodeType can declare shared=@OtherSpace/... source queries to reuse a code library published in another Space. Previously, on partitioned PostgreSQL deployments the whole bundle of source queries was searched only in the first query's Space, so shared sources from a different Space silently came back empty and the type failed to compile against them.

Multi-query searches now route every query to the Space that owns it and merge the results, so cross-partition shared-source libraries (for example a shared business-rules scope library) work exactly like same-Space ones — no need to copy the files into your own Space anymore.