Naively implement spec change 24fb00c9f0ca1ed63113

Setty.list returns keys, whereas Baggy/Mixy.list return pairs.  This causes
some smartmatching and set operators to return "unexpected" results in roast.
Investigating whether this would require change of the spec (Setty.list also
returning pairs) or changes in the set operators / smart matching.

src/core/Baggy.pm

@@ -73,7 +73,7 @@ my role Baggy does QuantHash {
         ~ ").{self.^name}"
     }
 
-    method list() { self.keys }
+    method list() { self.pairs }
     method pairs() { %!elems.values.map: { (.key => .value) } }
 
     method grab ($count = 1) {