job-manager: publish event on jobtap exception

Problem: the job manager publishes a job-exception event message
when an exception is raised via the job-manager.raise RPC, but not
when a jobtap plugin calls flux_jobtap_raise_exception().

Publish the job-exception event when a jobtap plugin calls
flux_jobtap_raise_exception().

Fixes flux-framework#5306

src/modules/job-manager/jobtap.c

@@ -1931,6 +1931,18 @@ static int jobtap_job_vraise (struct jobtap *jobtap,
     char note [1024];
     if (vsnprintf (note, sizeof (note), fmt, ap) >= sizeof (note))
         note[sizeof(note) - 2] = '+';
+
+    flux_future_t *f;
+    if (!(f = flux_event_publish_pack (jobtap->ctx->h,
+                                       "job-exception",
+                                       FLUX_MSGFLAG_PRIVATE,
+                                       "{s:I s:s s:i}",
+                                       "id", job->id,
+                                       "type", type,
+                                       "severity", severity)))
+        return -1;
+    flux_future_destroy (f);
+
     return event_job_post_pack (jobtap->ctx->event,
                                 job, "exception", 0,
                                 "{ s:s s:i s:i s:s }",