When we used the tool multi-fe to start multiple FEs cluster and loaded data by stream load way,
the request failed. See the following log.
The issue was caused by the netty libraries.
There are multiple netty libraries in classpath and the FE used the newer version netty library which made these errors.
Introduce a tool to start multiple FEs on single node.
Use case:
```
$ ./multi-fe
./multi-fe start|stop|clean [OPTIONS ...]
start -n <NUM> -l <LIBRARY_PATH> -p <BASE_PORT>
Start the FE cluster.
-n The number of FEs.
-l The FE library path (default: doris/output/fe/lib)
-p The base port to generate all needed ports (default: 9030).
stop Stop the FE cluster.
clean Stop the data (rm -rf "$(pwd)"/fe*).
```
