Move IR interpreter's tests from ir/loweredIr directory into box

compiler/testData/codegen/box/involvesIrInterpreter/stringConcatenationWithObject.kt

@@ -0,0 +1,15 @@
+// TARGET_BACKEND: JVM_IR
+
+object K : Code("K")
+
+open class Code(val x: String) {
+    override fun toString() = "$x"
+}
+
+class O {
+    companion object: Code("O")
+}
+
+fun box(): String {
+    return "$O" + "$K" // must not be evaluated during compile time
+}