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/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -11216,6 +11216,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                     doTest(fileName);
                 }
 
+                @TestMetadata("irrelevantCharAtAbstract.kt")
+                public void testIrrelevantCharAtAbstract() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/j+k/collectionOverrides/irrelevantCharAtAbstract.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("irrelevantImplCharSequence.kt")
                 public void testIrrelevantImplCharSequence() throws Exception {
                     String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/j+k/collectionOverrides/irrelevantImplCharSequence.kt");
@@ -11240,6 +11246,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                     doTest(fileName);
                 }
 
+                @TestMetadata("irrelevantMapGetAbstract.kt")
+                public void testIrrelevantMapGetAbstract() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/j+k/collectionOverrides/irrelevantMapGetAbstract.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("mapGetOverride.kt")
                 public void testMapGetOverride() throws Exception {
                     String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/j+k/collectionOverrides/mapGetOverride.kt");