replace restore_size_trail by more generic restore_vector

other updates:
- change signature of advance_qhead to simplify call sites
- have model reconstruction replay work on a tail of dependent_expr state, while adding formulas to the tail.

src/ast/simplifiers/card2bv.cpp

@@ -49,7 +49,7 @@ void card2bv::reduce() {
     for (func_decl* f : fns)
         m_fmls.model_trail().hide(f);    
 
-     advance_qhead(m_fmls.size());
+     advance_qhead();
 }
 
 void card2bv::collect_statistics(statistics& st) const {