Polysat: constraint refactor cont'd, deduplicate constraints (#5520)

* Assign boolean variables only to long-lived constraints, and deduplicate constraints when they are created

* scoped_signed_constraint

* update other classes

* fix

* Don't use scoped_ptr<constraint> with dedup()

src/math/polysat/explain.cpp

@@ -561,4 +561,7 @@ namespace polysat {
 //         return true;
 //     }
 
+    void conflict_explainer::resolve()
+    {
+    }
 }