Fix signature clash problems caused by special built-ins

Do not treat members with already changed signature as a reason
to create a hidden copy

See tests for clarification:
- There are `charAt` method in B that has different name in Kotlin - `get`,
  i.e. relevant descriptor has initialSignatureDescriptor != null
- When collecting methods from supertypes, `charAt` from A is also get
  transformed to `get`
- So it has effectively the same signature as B.get (already declared)
- If by an accident B.get had been declared with Kotlin signature
  we would have add A.charAt (after transformation) with special flag:
  HiddenToOvercomeSignatureClash (hides it from resolution)
- But here B.charAt was artificially changed to `get`, so no signature clash
  actually happened

 #KT-13730 Fixed

compiler/tests-java8/tests/org/jetbrains/kotlin/checkers/DiagnosticsWithJava8TestGenerated.java

@@ -98,6 +98,21 @@ public class DiagnosticsWithJava8TestGenerated extends AbstractDiagnosticsWithFu
         }
     }
 
+    @TestMetadata("compiler/testData/diagnostics/testsWithJava8/specialBuiltIns")
+    @TestDataPath("$PROJECT_ROOT")
+    @RunWith(JUnit3RunnerWithInners.class)
+    public static class SpecialBuiltIns extends AbstractDiagnosticsWithFullJdkTest {
+        public void testAllFilesPresentInSpecialBuiltIns() throws Exception {
+            KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/diagnostics/testsWithJava8/specialBuiltIns"), Pattern.compile("^(.+)\\.kt$"), true);
+        }
+
+        @TestMetadata("hashtableInheritance.kt")
+        public void testHashtableInheritance() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/testsWithJava8/specialBuiltIns/hashtableInheritance.kt");
+            doTest(fileName);
+        }
+    }
+
     @TestMetadata("compiler/testData/diagnostics/testsWithJava8/statics")
     @TestDataPath("$PROJECT_ROOT")
     @RunWith(JUnit3RunnerWithInners.class)