fix(meta): add back host, a deprecated cmd line argument (#7616)

risingwave-operator made a [temporary fix](risingwavelabs/risingwave-operator@f011c36) with regards to the breaking change that uses `meta-endpoint` instead of `host`, please refer to #7527.
But the cloud is unable to adopt this change right now, so we add `host` back.


By looking at the temporary fix, it used to use `IP` as `host` and now uses `IP:PORT` as `meta-endpoint`.
So this hot fix uses `IP` from `host` and  `PORT` from `listening-addr` to compose `meta-endpoint`, please correct me if I am wrong.

Approved-By: arkbriar
Approved-By: jon-chuang

src/meta/src/lib.rs

@@ -66,6 +66,10 @@ pub struct MetaNodeOpts {
     #[clap(long, default_value = "127.0.0.1:5690")]
     listen_addr: String,
 
+    /// Deprecated. But we keep it for backward compatibility.
+    #[clap(long)]
+    host: Option<String>,
+
     /// The endpoint for this meta node, which also serves as its unique identifier in cluster
     /// membership and leader election.
     #[clap(long)]
@@ -120,6 +124,7 @@ pub struct MetaNodeOpts {
 }
 
 use std::future::Future;
+use std::net::SocketAddr;
 use std::pin::Pin;
 
 use risingwave_common::config::load_config;
@@ -132,13 +137,14 @@ pub fn start(opts: MetaNodeOpts) -> Pin<Box<dyn Future<Output = ()> + Send>> {
         let config = load_config(&opts.config_path);
         tracing::info!("Starting meta node with config {:?}", config);
         tracing::info!("Starting meta node with options {:?}", opts);
-        let listen_addr = opts.listen_addr.parse().unwrap();
+        let listen_addr: SocketAddr = opts.listen_addr.parse().unwrap();
+        let meta_addr = opts.host.unwrap_or_else(|| opts.listen_addr.clone());
         let dashboard_addr = opts.dashboard_host.map(|x| x.parse().unwrap());
         let prometheus_addr = opts.prometheus_host.map(|x| x.parse().unwrap());
         let (meta_endpoint, backend) = match opts.backend {
             Backend::Etcd => (
                 opts.meta_endpoint
-                    .expect("meta_endpoint must be specified when using etcd"),
+                    .unwrap_or_else(|| format!("{}:{}", meta_addr, listen_addr.port())),
                 MetaStoreBackend::Etcd {
                     endpoints: opts
                         .etcd_endpoints