Handle methods descriptor clash in data class

1. Extension functions declared in data classes are generated earlier by `generateMembersDeclaredInClassBody`
2. Extension functions fake override from parent class are generated earlier by `generateFakeOverrideMemberDeclarations`

So it is safe to filter out extension functions inside `generateAdditionalMembersForDataClass`

 #KT-49715
 #KT-51798

native/native.tests/tests-gen/org/jetbrains/kotlin/konan/blackboxtest/NativeCodegenBoxTestGenerated.java

@@ -10681,6 +10681,12 @@ public class NativeCodegenBoxTestGenerated extends AbstractNativeCodegenBoxTest
                 runTest("compiler/testData/codegen/box/dataClasses/genericParam.kt");
             }
 
+            @Test
+            @TestMetadata("kt49715.kt")
+            public void testKt49715() throws Exception {
+                runTest("compiler/testData/codegen/box/dataClasses/kt49715.kt");
+            }
+
             @Test
             @TestMetadata("mixedParams.kt")
             public void testMixedParams() throws Exception {