Add simplification customization for SMTLIB2

Add the ability to customize incremental pre-processing simplification for the SMTLIB2 front-end. The main new capability is to use pre-processing tactics in incremental mode that were previously not available. The main new capabilities are
- solve-eqs
- reduce-args
- elim-unconstrained
There are several more. Documentation and exposed simplifiers are populated incrementally. The current set of supported simplifiers can be inspected by using z3 with the --simplifiers flag or referring to https://microsoft.github.io/z3guide/docs/strategies/simplifiers

Some pending features are:
- add the ability to update parameters to simplifiers similar to how tactics can be controlled using parameters.
- expose simplification solvers over the binary API.

src/sat/sat_solver/sat_smt_solver.cpp

@@ -700,6 +700,6 @@ private:
 
 
 solver* mk_sat_smt_solver(ast_manager& m, params_ref const& p) {
-    return mk_simplifier_solver(alloc(sat_smt_solver, m, p));
+    return mk_simplifier_solver(alloc(sat_smt_solver, m, p), nullptr);
 }