chore: Remove unused RouterType and ModelMetaData (#1138)

Remove RouterType and ModelMetaData in `lib/runtime/src/protocols.rs`, which are unused (no outside reference). It is because that the routing has been moved to its own module, `pipeline/network/egress/push_router.rs`. Therefore, the legacy definition of RouterType in `protocols.rs` is no longer used.

lib/runtime/src/protocols.rs

@@ -183,59 +183,12 @@ impl Endpoint {
     }
 }
 
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq)]
-#[serde(rename_all = "snake_case")]
-pub enum RouterType {
-    PushRoundRobin,
-    PushRandom,
-}
-
-impl Default for RouterType {
-    fn default() -> Self {
-        Self::PushRandom
-    }
-}
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq)]
-pub struct ModelMetaData {
-    pub name: String,
-    pub component: Component,
-    pub router_type: RouterType,
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
     use std::convert::TryFrom;
     use std::str::FromStr;
 
-    #[test]
-    fn test_router_type_default() {
-        let default_router = RouterType::default();
-        assert_eq!(default_router, RouterType::PushRandom);
-    }
-
-    #[test]
-    fn test_router_type_serialization() {
-        let router_round_robin = RouterType::PushRoundRobin;
-        let router_random = RouterType::PushRandom;
-
-        let serialized_round_robin = serde_json::to_string(&router_round_robin).unwrap();
-        let serialized_random = serde_json::to_string(&router_random).unwrap();
-
-        assert_eq!(serialized_round_robin, "\"push_round_robin\"");
-        assert_eq!(serialized_random, "\"push_random\"");
-    }
-
-    #[test]
-    fn test_router_type_deserialization() {
-        let round_robin: RouterType = serde_json::from_str("\"push_round_robin\"").unwrap();
-        let random: RouterType = serde_json::from_str("\"push_random\"").unwrap();
-
-        assert_eq!(round_robin, RouterType::PushRoundRobin);
-        assert_eq!(random, RouterType::PushRandom);
-    }
-
     #[test]
     fn test_valid_endpoint_from() {
         let input = "namespace1/component1/endpoint1";