EndToEndTests should test a larger set of core libraries

[euanh]

We should test more of the core libraries here: FoundationEssentials, FoundationInternationalization, FoundationNetworking, FoundationXML, Dispatch, RegexBuilder, Synchronization, and Observation maybe. Since these are separate modules and are linked separately, we need to make sure that all necessary files are copied and discovered correctly.

Originally posted by @MaxDesiatov in #155 (comment)

[xtremekforever]

This would be good, because I found that the Swift SDKs are missing curl for static linking of FoundationNetworking: #197