Generate private methods in TraitImpl as private, don't generate delegation to private trait methods

compiler/testData/codegen/box/traits/noPrivateDelegation.kt

@@ -0,0 +1,16 @@
+interface Z{
+
+    private fun extension(): String {
+        return "OK"
+    }
+}
+
+object Z2 : Z {
+
+}
+
+fun box() : String {
+    val size = Class.forName("Z2").declaredMethods.size
+    if (size != 0) return "fail: $size"
+    return "OK"
+}

compiler/testData/codegen/box/traits/syntheticAccessor.kt

@@ -0,0 +1,21 @@
+var result = "fail"
+
+interface B {
+
+    private fun test() {
+        result = "OK"
+    }
+
+    class Z {
+        fun ztest(b: B) {
+            b.test()
+        }
+    }
+}
+
+class C : B
+
+fun box(): String {
+    B.Z().ztest(C())
+    return result
+}