backend/tests: Add blackbox tests from Kotlin JVM

Added tests from testData/codegen/box directory. There are blackbox tests
in other directories and they are to be added.

backend.native/tests/external/codegen/blackbox/fakeOverride/diamondFunction.kt

@@ -0,0 +1,31 @@
+interface T {
+    fun foo(): Unit
+}
+
+open class A : T {
+    override fun foo() {}
+}
+
+interface B : T
+
+class C : A(), B
+class D : B, A()
+class E : A(), B, T
+class F : B, A(), T
+class G : A(), T, B
+class H : B, T, A()
+class I : T, A(), B
+class J : T, B, A()
+
+fun box(): String {
+    C().foo()
+    D().foo()
+    E().foo()
+    F().foo()
+    G().foo()
+    H().foo()
+    I().foo()
+    J().foo()
+
+    return "OK"
+}

backend.native/tests/external/codegen/blackbox/fakeOverride/function.kt

@@ -0,0 +1,35 @@
+interface T {
+    fun foo(): Unit
+}
+
+open class A : T {
+    override fun foo(): Unit {}
+}
+
+class B : A(), T
+class C : T, A()
+
+interface U : T
+class D : U, A()
+class E : A(), U
+class F : U, T, A()
+class G : T, U, A()
+class H : U, A(), T
+class I : T, A(), U
+class J : A(), U, T
+class K : A(), T, U
+
+fun box(): String {
+    B().foo()
+    C().foo()
+    D().foo()
+    E().foo()
+    F().foo()
+    G().foo()
+    H().foo()
+    I().foo()
+    J().foo()
+    K().foo()
+
+    return "OK"
+}

backend.native/tests/external/codegen/blackbox/fakeOverride/propertyGetter.kt

@@ -0,0 +1,37 @@
+interface T {
+    val foo: String
+}
+
+open class A : T {
+    override val foo: String = ""
+}
+
+class B : A(), T
+class C : T, A()
+
+interface U : T
+
+class D : U, A()
+class E : A(), U
+class F : U, T, A()
+class G : T, U, A()
+class H : U, A(), T
+class I : T, A(), U
+class J : A(), U, T
+class K : A(), T, U
+
+fun box(): String {
+    B().foo
+    C().foo
+
+    D().foo
+    E().foo
+    F().foo
+    G().foo
+    H().foo
+    I().foo
+    J().foo
+    K().foo
+
+    return "OK"
+}

backend.native/tests/external/codegen/blackbox/fakeOverride/propertySetter.kt

@@ -0,0 +1,18 @@
+interface T {
+    var result: String
+}
+
+open class A : T {
+    override var result: String
+        get() = ""
+        set(value) {}
+}
+
+class B : A(), T
+class C : T, A()
+
+fun box(): String {
+    B().result = ""
+    C().result = ""
+    return "OK"
+}