Introduce UNUSED_ANONYMOUS_PARAMETER for anonymous functions

It is not reported for 1.0 language version because
renaming to _ is not possible. It has weak warning severity

So #KT-8813 Fixed
So #KT-16875 Fixed

compiler/testData/diagnostics/tests/inference/dependantOnVarianceNullable.kt

@@ -5,7 +5,7 @@ import java.util.*
 import java.util.Collections.*
 
 fun foo(list: List<String>) : String {
-    val w : String = max(list, comparator<String?> {<!UNUSED_PARAMETER!>o1<!>, <!UNUSED_PARAMETER!>o2<!> -> 1
+    val w : String = max(list, comparator<String?> {<!UNUSED_ANONYMOUS_PARAMETER!>o1<!>, <!UNUSED_ANONYMOUS_PARAMETER!>o2<!> -> 1
     })
     return w
 }