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

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

@@ -0,0 +1,17 @@
+// TARGET_BACKEND: JVM_IR
+// WITH_STDLIB
+
+object Test {
+    fun foo(): String = "foo " + this
+
+    fun bar(): String = "bar $this"
+
+    fun baz(): String = "baz " + this.toString()
+}
+
+fun box(): String {
+    if (!Test.foo().startsWith("foo ")) return "Fail ${Test.foo()}"
+    if (!Test.bar().startsWith("bar ")) return "Fail ${Test.bar()}"
+    if (!Test.baz().startsWith("baz ")) return "Fail ${Test.baz()}"
+    return "OK"
+}