Fix issues with Int.new

- Fix wrong error (default constructor blah blah) with wrong args
- Fix subclassed Ints returning an Int instead of subclass

Fixes RT#132128: https://rt.perl.org/Ticket/Display.html?id=132128

src/core/Int.pm

@@ -22,11 +22,15 @@ my class Int does Real { # declared in BOOTSTRAP
           ObjAt
         )
     }
-    multi method new($value) {
-        # clone to ensure we return a new object for any cached
-        # numeric constants
-        $value.Int.clone;
+
+    proto method new(|) {*}
+    multi method new(      \value) { self.new: value.Int         }
+    multi method new(int   \value) { nqp::box_i(value,self.WHAT) }
+    multi method new(Int:D \value = 0) {
+        nqp::p6bindattrinvres(self.bless, Int,'$!value',
+          nqp::getattr(nqp::decont(value),Int,'$!value'))
     }
+
     multi method perl(Int:D:) {
         self.Str;
     }