Fix concrete method inheritance in interfaces

For each non-abstract non-declared (i.e. inherited from supertypes) method in
an interface we generate its static form to the TImpl, which calls the TImpl
method from the corresponding supertype.

The accidental override tests changed because we're now trying to generate the
delegate for the super method, not knowing that it will clash with the declared
method

 #KT-2888 Fixed
 #KT-5393 Fixed

compiler/testData/codegen/box/traits/kt5393.kt

@@ -0,0 +1,17 @@
+interface A {
+    fun foo(): String {
+        return "OK"
+    }
+}
+
+interface B : A
+
+class C : B {
+    override fun foo(): String {
+        return super.foo()
+    }
+}
+
+fun box(): String {
+    return C().foo()
+}

compiler/testData/codegen/box/traits/kt5393_property.kt

@@ -0,0 +1,20 @@
+var result = "Fail"
+
+interface A {
+    var foo: String
+        get() = result
+        set(value) { result = value }
+}
+
+interface B : A
+
+class C : B {
+    override var foo: String
+        get() = super.foo
+        set(value) { super.foo = value }
+}
+
+fun box(): String {
+    C().foo = "OK"
+    return C().foo
+}

compiler/testData/codegen/box/traits/kt5393_toString.kt

@@ -0,0 +1,15 @@
+interface A {
+    override fun toString(): String {
+        return "OK"
+    }
+}
+
+interface B : A
+
+class C : B {
+    override fun toString(): String {
+        return super.toString()
+    }
+}
+
+fun box() = "${C()}"

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

@@ -0,0 +1,18 @@
+interface A {
+    fun foo(): Number {
+        return 42
+    }
+}
+
+interface B : A
+
+class C : B {
+    override fun foo(): Int {
+        return super.foo() as Int
+    }
+}
+
+fun box(): String {
+    val x = C().foo()
+    return if (x == 42) "OK" else "Fail: $x"
+}

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

@@ -0,0 +1,15 @@
+interface A {
+    fun foo() = "Fail"
+}
+
+interface B : A
+
+interface C : A {
+    override fun foo() = "OK"
+}
+
+interface D : B, C
+
+class Impl : D
+
+fun box(): String = Impl().foo()

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

@@ -0,0 +1,18 @@
+interface A<T, U : Number, V : Any> {
+    fun foo(t: T, u: U): V? {
+        return null
+    }
+}
+
+interface B<T, V : Any> : A<T, Int, V>
+
+class C : B<String, Runnable> {
+    override fun foo(t: String, u: Int): Runnable? {
+        return super.foo(t, u)
+    }
+}
+
+fun box(): String {
+    val x = C().foo("", 0)
+    return if (x == null) "OK" else "Fail: $x"
+}