Remove backend tests on old inference

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

compiler/testData/codegen/box/funInterface/basicFunInterfaceConversion.kt

@@ -1,5 +1,3 @@
-// !LANGUAGE: +NewInference +FunctionalInterfaceConversion +SamConversionPerArgument +SamConversionForKotlinFunctions
-
 fun interface Foo {
     fun invoke(): String
 }
@@ -8,4 +6,4 @@ fun foo(f: Foo) = f.invoke()
 
 fun box(): String {
     return foo { "OK" }
-}
+}