Investigate potential over-emission of force load symbols

[compnerd]

While cleaning up the SPM build, I noticed that there was a significant amount of over-linking for libraries. The primary driver for this was the over-use of force load symbols which forced the dependency preservation over a large area of the Swift PM codebase without any use of public functions. We should ensure that this is not a bug in the compiler that is forcing extra libraries to be persisted and loaded into the address space unnecessarily.