[Native] Don't group K2 MPP tests in Native codegen tests

K2 in MPP compilation expects that it receives module structure
  with exactly one platform leaf module. This invariant may be broken
  during grouping tests, so MPP tests should be run in standalone mode

native/native.tests/tests/org/jetbrains/kotlin/konan/test/blackbox/support/group/ExtTestCaseGroupProvider.kt

@@ -207,6 +207,12 @@ private class ExtTestDataFile(
             directives.contains(IGNORE_NATIVE_K2.name)
         ) return true
 
+        /**
+         * K2 in MPP compilation expects that it receives module structure with exactly one platform leaf module
+         * This invariant may be broken during grouping tests, so MPP tests should be run in standalone mode
+         */
+        if (pipelineType != PipelineType.K1 && testDataFileSettings.languageSettings.contains("+MultiPlatformProjects")) return true
+
         var isStandaloneTest = false
 
         filesToTransform.forEach { handler ->