Add a timeout to runOnce

This allows runOnce to be interwoven with other polling mechanisms.

src/syndicate/actors.nim

@@ -745,16 +745,16 @@ proc runPendingTurns* =
       terminateActor(turn, err)
       raise err
 
-proc runOnce*: bool {.discardable.} =
+proc runOnce*(timeout = none(Duration)): bool {.discardable.} =
   ## Run pending turns if there are any, otherwise
   ## poll for external events and run any resulting turns.
   ## Return true if any turns have been processed.
   if turnQueue.len == 0:
     when defined(solo5):
-      discard solo5_dispatcher.runOnce()
+      discard solo5_dispatcher.runOnce(timeout)
     else:
       var ready: seq[Continuation]
-      ioqueue.poll(ready)
+      ioqueue.poll(ready, timeout)
       while ready.len > 0:
         discard trampoline:
           ready.pop()
@@ -764,7 +764,7 @@ proc runOnce*: bool {.discardable.} =
 proc run* =
   ## Run actors to completion.
   when defined(solo5):
-    while turnQueue.len > 0 or solo5_dispatcher.runOnce():
+    while turnQueue.len > 0 or solo5_dispatcher.runOnce(timeout):
       runPendingTurns()
   else:
     var ready: seq[Continuation]