Move legacy assert tests to launcher

since they are broken on JDK 11: they change Field.modifiers, which is prohibited
since JDK 9, because this private field is not exported.
Thus, we need to split the test into two: one with assertions enabled and the other
one with them disabled. Also, we need to run them in separate processes, for them
not to interfere each other.
 #KT-27176 Fixed

compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java

@@ -896,11 +896,6 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             runTest("compiler/testData/codegen/box/assert/alwaysEnable.kt");
         }
 
-        @TestMetadata("legacy.kt")
-        public void testLegacy() throws Exception {
-            runTest("compiler/testData/codegen/box/assert/legacy.kt");
-        }
-
         @TestMetadata("compiler/testData/codegen/box/assert/jvm")
         @TestDataPath("$PROJECT_ROOT")
         @RunWith(JUnit3RunnerWithInners.class)