Remove backend tests on old inference

Also remove any mentions of NewInference, and rename some tests.

compiler/testData/codegen/box/functions/functionExpression/functionExpressionWithThisReference.kt

@@ -1,4 +1,3 @@
-
 fun Int.thisRef1() = fun () = this
 fun Int.thisRef2() = fun (): Int {return this}
 
@@ -31,4 +30,4 @@ fun box(): String {
     if ("bar".withLabel2() != "bar") return "Test 10 failed"
 
     return "OK"
-}
+}