add bounded-int and pb2bv solvers to fd_solver, use sorting networks for pb2bv rewriter when applicable, hoist to pb2bv_rewriter module and remove it from the pb2bv_tactic

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/cmd_context/cmd_context.cpp

@@ -547,6 +547,7 @@ bool cmd_context::logic_has_arith_core(symbol const & s) const {
         s == "QF_BVFP" ||
         s == "QF_S" ||
         s == "ALL" ||
+        s == "QF_FD" || 
         s == "HORN";
 }