Remove backend tests on old inference

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

compiler/testData/ir/irText/regressions/newInferenceFixationOrder1.kt

@@ -0,0 +1,14 @@
+// FIR_IDENTICAL
+fun <X, Y> foo(): (X) -> Y = TODO()
+
+interface Inv2<A, B>
+
+fun <T, R> check(x: T, y: R, f: (T) -> R): Inv2<T, R> = TODO()
+
+fun test() = check("", 1, foo())
+
+fun box(): String {
+    val x: Inv2<String, Int> = test()
+
+    return "OK"
+}