Remove backend tests on old inference

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

compiler/testData/codegen/box/package/referenceWithTheSameNameAsPackage.kt

@@ -1,6 +1,4 @@
-// !LANGUAGE: +NewInference
 // WITH_RUNTIME
-
 // FILE: messages/foo.kt
 
 package messages
@@ -20,4 +18,4 @@ class Test {
 fun box(): String {
     val result = Test().test()
     return if (result) "faile" else "OK"
-}
+}