Move responsibility for threadpool reply-handler events to workqueue

This change makes cpuworker and test_workqueue no longer need to
include event2/event.h.  Now workqueue.c needs to include it, but
that is at least somewhat logical here.

src/test/test_workqueue.c

@@ -12,7 +12,6 @@
 #include "compat_libevent.h"
 
 #include <stdio.h>
-#include <event2/event.h>
 
 #define MAX_INFLIGHT (1<<16)
 
@@ -159,6 +158,7 @@ static tor_weak_rng_t weak_rng;
 static int n_sent = 0;
 static int rsa_sent = 0;
 static int ecdh_sent = 0;
+static int n_received_previously = 0;
 static int n_received = 0;
 static int no_shutdown = 0;
 
@@ -256,19 +256,13 @@ add_n_work_items(threadpool_t *tp, int n)
 static int shutting_down = 0;
 
 static void
-replysock_readable_cb(tor_socket_t sock, short what, void *arg)
+replysock_readable_cb(threadpool_t *tp)
 {
-  threadpool_t *tp = arg;
-  replyqueue_t *rq = threadpool_get_replyqueue(tp);
-
-  int old_r = n_received;
-  (void) sock;
-  (void) what;
-
-  replyqueue_process(rq);
-  if (old_r == n_received)
+  if (n_received_previously == n_received)
     return;
 
+  n_received_previously = n_received;
+
   if (opt_verbose) {
     printf("%d / %d", n_received, n_sent);
     if (opt_n_cancel)
@@ -337,7 +331,6 @@ main(int argc, char **argv)
   threadpool_t *tp;
   int i;
   tor_libevent_cfg evcfg;
-  struct event *ev;
   uint32_t as_flags = 0;
 
   for (i = 1; i < argc; ++i) {
@@ -411,11 +404,11 @@ main(int argc, char **argv)
   memset(&evcfg, 0, sizeof(evcfg));
   tor_libevent_initialize(&evcfg);
 
-  ev = tor_event_new(tor_libevent_get_base(),
-                     replyqueue_get_socket(rq), EV_READ|EV_PERSIST,
-                     replysock_readable_cb, tp);
-
-  event_add(ev, NULL);
+  {
+    int r = threadpool_register_reply_event(tp,
+                                            replysock_readable_cb);
+    tor_assert(r == 0);
+  }
 
 #ifdef TRACK_RESPONSES
   handled = bitarray_init_zero(opt_n_items);