fix #6591

- add check for lambdas similar to as-array in context of quantifiers. MBQI is not a decision procedure for this combination and can then incorrectly conclude satisfiabiltiy.

Scenario

The formula contains assertions
 - bv = (map or (lambda ..) t)
 - forall y (not (select bv (pair s y)))

Since bv is extensionally equal to a term that depends on a lambda, MBQI cannot just take the current finite approximation of bv when checking the quantifier for satisfiability.

src/smt/theory_array_full.h

@@ -86,6 +86,7 @@ namespace smt {
         bool has_unitary_domain(app* array_term);
         std::pair<app*,func_decl*> mk_epsilon(sort* s);
         enode_vector m_as_array;
+        enode_vector m_lambdas;
         bool has_non_beta_as_array();
 
         bool instantiate_select_const_axiom(enode* select, enode* cnst);