optimize memory issues (#767)

* optimize memory issues

1. introduce jemalloc support, which can dump current memory usage
2. reduce the GlobalEvent broadcaster memory usage.
3. reduce tcp & udp tunnel memory usage

TODO: if peer conn tunnel hangs, the unbounded channel of peer rpc
may consume lots of memory, which should be improved.

* select a port from 15888+ when port is 0

easytier-web/frontend-lib/src/types/network.ts

@@ -93,7 +93,7 @@ export function DEFAULT_NETWORK_CONFIG(): NetworkConfig {
       'udp://0.0.0.0:11010',
       'wg://0.0.0.0:11011',
     ],
-    rpc_port: 15888,
+    rpc_port: 0,
     latency_first: false,
     dev_name: '',