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/extensionFunctions/whenFail.kt

@@ -0,0 +1,27 @@
+// TODO: muted automatically, investigate should it be ran for JS or not
+// IGNORE_BACKEND: JS
+
+fun StringBuilder.takeFirst(): Char {
+  if (this.length == 0) return 0.toChar()
+  val c = this.get(0)
+  this.deleteCharAt(0)
+  return c
+}
+
+fun foo(expr: StringBuilder): Int {
+  val c = expr.takeFirst()
+  when(c) {
+    0.toChar() -> throw Exception("zero")
+    else -> throw Exception("nonzero" + c)
+  }
+}
+
+fun box(): String {
+  try {
+    foo(StringBuilder())
+    return "Fail"
+  }
+  catch (e: Exception) {
+    return "OK"
+  }
+}