Host-less unit tests run separately instead of crashing the workspace scheme

When a default tuist test run hits a generated workspace scheme that mixes app-hosted and host-less unit test bundles, Tuist no longer runs them from the workspace aggregate scheme (which crashes xctest at bootstrap on Xcode 26.5). It runs the matching generated project schemes one after another and filters --test-targets and --skip-test-targets per split scheme so selected tests stay scoped to the right bundle.