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/binaryOp/compareWithBoxedDouble.kt

@@ -0,0 +1,17 @@
+// IGNORE_BACKEND: JS
+// reason - multifile tests are not supported in JS tests
+//FILE: Holder.java
+
+class Holder {
+    public Double value;
+    public Holder(Double value) { this.value = value; }
+}
+
+//FILE: test.kt
+
+import Holder
+
+fun box(): String {
+    val j = Holder(0.99)
+    return if (j.value > 0) "OK" else "fail"
+}