Use constraint system for comparing for specificity against a generic signature.

Drop "discrimiate generics" mode where it's unneeded.

compiler/testData/diagnostics/tests/resolve/overloadConflicts/varargsWithRecursiveGenerics.kt

@@ -0,0 +1,21 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+// FILE: J.java
+import java.util.*
+
+public class J {
+    public static <E1 extends Enum<E1>> String foo(E1 e) { return ""; }
+    public static <E2 extends Enum<E2>> String foo(E2 e1, E2 e2) { return ""; }
+    public static <E3 extends Enum<E3>> String foo(E3 s1, E3 s2, E3 s3) { return ""; }
+    public static <E4 extends Enum<E4>> int foo(E4... ss) { return 0; }
+}
+
+// FILE: test.kt
+enum class X { A }
+val a = X.A
+
+val test0: Int = J.foo<X>()
+val test1: String = J.foo(a)
+val test2: String = J.foo(a, a)
+val test3: String = J.foo(a, a, a)
+val test4: Int = J.foo(a, a, a, a)
+val test5: Int = J.foo(a, a, a, a, a)