Move event.h into ipc_lib

Makes tab completion a lot less annoying.

Change-Id: I0c905ba112c274d23b5f0277b9a5c2a8e4e238f6
diff --git a/aos/network/BUILD b/aos/network/BUILD
index 3cb5c26..e42552d 100644
--- a/aos/network/BUILD
+++ b/aos/network/BUILD
@@ -340,11 +340,11 @@
     deps = [
         ":message_bridge_client_lib",
         ":message_bridge_server_lib",
-        "//aos:event",
         "//aos:json_to_flatbuffer",
         "//aos/events:ping_fbs",
         "//aos/events:pong_fbs",
         "//aos/events:shm_event_loop",
+        "//aos/ipc_lib:event",
         "//aos/testing:googletest",
     ],
 )