Module Cache support for library products

Module Cache can now cache static and dynamic library targets, not only framework targets. Library products are warmed, stored, and consumed as XCFramework artifacts, including Swift modules and public headers, so projects with mixed framework and library graphs can reuse binary cache artifacts across local and CI builds.

Test bundles remain excluded from the binary cache, but reusable library targets that support tests can now benefit from the same cache flow as test-support frameworks.