EventLoop: added assert(IsInside()) in Insert(CoarseTimerEvent &) and AddIdle(DeferEvent &)

Like AddDefer(DeferEvent &), Insert(FineTimerEvent &), these methods don't lock to update EventLoop::again

src/event/Loop.cxx

@@ -151,6 +151,8 @@ EventLoop::AbandonFD(SocketEvent &event)  noexcept
 void
 EventLoop::Insert(CoarseTimerEvent &t) noexcept
 {
+	assert(IsInside());
+
 	coarse_timers.Insert(t, SteadyNow());
 	again = true;
 }
@@ -192,6 +194,8 @@ EventLoop::AddDefer(DeferEvent &e) noexcept
 void
 EventLoop::AddIdle(DeferEvent &e) noexcept
 {
+	assert(IsInside());
+
 	idle.push_back(e);
 	again = true;
 }