KT-2752: add diagnostics that reports about conflicting overridden declarations

compiler/testData/codegen/box/bridges/jsNative.kt

@@ -0,0 +1,28 @@
+// TARGET_BACKEND: JS
+package foo
+
+@native interface A {
+    fun foo(value: Int): String
+}
+
+interface B {
+    fun foo(value: Int): String
+}
+
+class C : A, B {
+    override fun foo(value: Int) = "C.foo($value)"
+}
+
+fun box(): String {
+    val a: A = C()
+    assertEquals("C.foo(55)", a.foo(55))
+
+    val b: B = C()
+    assertEquals("C.foo(23)", b.foo(23))
+
+    val d: dynamic = C()
+    assertEquals("C.foo(42)", d.foo(42))
+    assertEquals("C.foo(99)", d.`foo_za3lpa$`(99))
+
+    return "OK"
+}