[rooch-server] rooch server start should support custom RPC port

[feliciss]

The server config:

impl Default for ServerConfig {
    fn default() -> Self {
        Self {
            host: "0.0.0.0".to_string(),
            port: 50051,
            proposer_address: None,
            sequencer_address: None,
            block_propose_duration_in_seconds: 5,
        }
    }
}

Should support custom RPC port, like starting the server with a port from input rooch server start --port 50001 to test local PRC config via MetaMask as chain_id variable is added #681.

Otherwise, the newly added RPC config through rooch env add command cannot be tested with MetaMask for a chain_id:

envs:
- chain_id: 20230103
  alias: default
  rpc: http://0.0.0.0:50051
  ws: null
- chain_id: 2001
  alias: ROH
  rpc: http://0.0.0.0:50001
  ws: null

[feliciss]

Same as rooch init -s command that only inits one RPC config:

envs:
- chain_id: 2002
  alias: custom
  rpc: http://0.0.0.0:50055
  ws: null