Host-less unit tests in workspace schemes now run in isolated project schemes

When a workspace’s autogenerated aggregate scheme contains host-less unit-test bundles alongside app-hosted ones, tuist test now runs the per-project schemes (app target, then feature scheme) instead of the mixed workspace scheme. The workspace scheme is left untouched when requested explicitly with --scheme. This fixes xctest bootstrap crashes on Xcode 26.5 when app-hosted and host-less test bundles are combined.