Rename directory for back-end tests

compiler/testData/codegen/box/functions/tailRecursion/insideElvis.kt

@@ -0,0 +1,10 @@
+tailRecursive fun test(counter : Int, a : Any) : Int? {
+    if (counter < 0) return null
+    if (counter == 0) return 777
+
+    return test(-1, "no tail") ?: test(-2, "no tail") ?: test(counter - 1, "tail")
+}
+
+fun box() : String =
+    if (test(100000, "test") == 777) "OK"
+    else "FAIL"