wip - adding context equation solver

the solve_eqs_tactic is to be replaced by a re-implementation that uses solve_eqs in the simplifiers directory.
The re-implementation should address efficiency issues with the previous code.
At this point it punts on low level proofs. The plan is to use coarser
dependency tracking instead of low level proofs for pre-processing. Dependencies can be converted into a proof hint representation that can be checked using a stronger checker.

src/ast/simplifiers/solve_context_eqs.h

@@ -0,0 +1,58 @@
+/*++
+Copyright (c) 2022 Microsoft Corporation
+
+Module Name:
+
+    solve_context_eqs.h
+
+Abstract:
+
+    simplifier for solving equations within a context
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2022-11-2.
+
+--*/
+
+
+#pragma once
+
+#include "ast/simplifiers/dependent_expr_state.h"
+#include "ast/simplifiers/extract_eqs.h"
+
+namespace euf {
+
+    class solve_eqs;
+    
+
+    class solve_context_eqs {
+
+        ast_manager&              m;
+        dependent_expr_state&     m_fmls;
+        solve_eqs&                m_solve_eqs;
+        expr_mark                 m_and_pos, m_and_neg, m_or_pos, m_or_neg;
+        expr_mark                 m_contains_v;
+        ptr_vector<expr>          m_todo;
+
+        typedef svector<std::pair<bool, expr*>> signed_expressions;
+
+        bool contains_v(expr* f) const { return m_contains_v.is_marked(f); }
+        bool is_safe_eq(expr* e);
+        bool is_safe_eq(unsigned recursion_depth, expr* f, bool sign, expr* e);
+        bool is_safe_eq(expr* f, expr* e) { return is_safe_eq(0, f, false, e); }
+        bool is_disjunctively_safe(unsigned recursion_depth, expr* f, bool sign, expr* e);
+        bool contains_conjunctively(expr* f, bool sign, expr* e, signed_expressions& conjuncts);
+        
+        void collect_nested_equalities(dependent_expr const& f, expr_mark& visited, dep_eq_vector& eqs);
+        void init_contains(expr* v);
+        
+
+    public:
+        
+        solve_context_eqs(solve_eqs& s);
+
+        void collect_nested_equalities(dep_eq_vector& eqs);
+
+    };
+}