wip - throttle AC completion, enable congruences over bound bodies

- AC completion which is exposed as an option to the new congruence closure core used roots of E-Graph which gets ordering of monomials out of sync.
- Added injective function handling to AC completion
- Move to model where all equations, also unit to unit are in completion
- throw in first level bound bodies into the E-graph to enable canonization on them.

src/ast/euf/euf_arith_plugin.cpp

@@ -30,6 +30,7 @@ namespace euf {
         m_add.set_undo(uadd);
         std::function<void(void)> umul = [&]() { m_undo.push_back(undo_t::undo_mul); };
         m_mul.set_undo(umul);
+        m_add.set_injective();
     }    
 
     void arith_plugin::register_node(enode* n) {