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/test/main.cpp

@@ -229,6 +229,7 @@ int main(int argc, char ** argv) {
     TST_ARGV(ddnf);
     TST(model_evaluator);
     TST(get_consequences);
+    TST(pb2bv);
     //TST_ARGV(hs);
 }