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/reflection/functions/simpleGetFunctions.kt

@@ -0,0 +1,26 @@
+// TODO: muted automatically, investigate should it be ran for JS or not
+// IGNORE_BACKEND: JS
+
+// WITH_REFLECT
+
+import kotlin.reflect.*
+
+open class A {
+    fun mem() {}
+    fun Int.memExt() {}
+}
+
+class B : A()
+
+fun box(): String {
+    val all = A::class.functions.map { it.name }.sorted()
+    assert(all == listOf("equals", "hashCode", "mem", "memExt", "toString")) { "Fail A functions: ${A::class.functions}" }
+
+    val declared = A::class.declaredFunctions.map { it.name }.sorted()
+    assert(declared == listOf("mem", "memExt")) { "Fail A declaredFunctions: ${A::class.declaredFunctions}" }
+
+    val declaredSubclass = B::class.declaredFunctions.map { it.name }.sorted()
+    assert(declaredSubclass.isEmpty()) { "Fail B declaredFunctions: ${B::class.declaredFunctions}" }
+
+    return "OK"
+}