Host-less unit tests isolated when workspace schemes mix test bundle kinds

tuist test no longer crashes with “Early unexpected exit, operation never finished bootstrapping” when the auto-generated workspace scheme mixes app-hosted and host-less unit test bundles. The default run keeps the workspace scheme for explicit –scheme invocations, but switches to running the generated project test schemes one at a time when the workspace scheme contains host-less unit tests, and filters –test-targets / –skip-test-targets per split scheme so FeatureTests does not accidentally run AppTests.