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/properties/const/interfaceCompanion.kt

@@ -0,0 +1,23 @@
+// TODO: muted automatically, investigate should it be ran for JS or not
+// IGNORE_BACKEND: JS
+
+// WITH_RUNTIME
+
+interface KInt {
+
+    companion object {
+        const val a = "a"
+        const val b = "b$a"
+    }
+}
+
+fun box(): String {
+    val a = KInt::class.java.getField("a").get(null)
+    val b = KInt::class.java.getField("b").get(null)
+
+    if (a !== KInt.a) return "fail 1: KInt.a !== KInt.Companion.a"
+    if (b !== KInt.b) return "fail 2: KInt.b !== KInt.Companion.b"
+    if (b !== "ba") return "fail 2: 'ba' !== KInt.Companion.b"
+
+    return "OK"
+}