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/functionFromStdlib.kt

@@ -0,0 +1,10 @@
+// TODO: muted automatically, investigate should it be ran for JS or not
+// IGNORE_BACKEND: JS
+
+// WITH_REFLECT
+
+fun doStuff(fn: String.() -> String) = "ok".fn()
+
+fun box(): String {
+    return doStuff(String::toUpperCase)
+}