Implement type inference for super initializers.

pkg/front_end/testcases/inference/super_initializer.dart.direct.expect

+library test;
+import self as self;
+import "dart:core" as core;
+
+class C extends self::B {
+  constructor •() → void
+    : super self::B::•(self::f<dynamic>())
+    ;
+}
+class B extends core::Object {
+  constructor •(core::int x) → void
+    : super core::Object::•()
+    ;
+}
+static method f<T extends core::Object>() → self::f::T
+  return null;
+static method main() → dynamic {}