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

compiler/testData/codegen/box/dataClasses/kt49715.kt

@@ -0,0 +1,22 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+// FIR status: [IR VALIDATION] Duplicate IR node: FUN GENERATED_DATA_CLASS_MEMBER name:toString
+// CHECK_BYTECODE_LISTING
+// WITH_STDLIB
+
+import kotlin.test.*
+
+interface A {
+    fun Any.toString(): String = "hello"
+}
+
+data class B(val x: Int) : A {
+    fun Any.hi() = "hi"
+}
+
+fun box(): String {
+    val b = B(1)
+    assertEquals("B(x=1)", b.toString())
+    assertTrue(b == B(1))
+    assertTrue(1.hashCode() == b.hashCode())
+    return "OK"
+}