Host-less unit tests no longer crash the mixed workspace scheme run

When an autogenerated workspace scheme contains a mix of app-hosted and host-less unit test bundles, the default tuist test run now executes the generated project schemes separately instead of the workspace aggregate. This avoids the xctest bootstrap crash users saw on Xcode 26.5 when the workspace aggregate tried to launch app-hosted and host-less bundles in the same context. Explicit tuist test –scheme… behavior is unchanged, and –test-targets / –skip-test-targets are filtered per split scheme.