Consolidate more extension API structs that were duplicated btwn client and server (#9797)

Release Notes:

- N/A

crates/rpc/src/extension.rs

@@ -1,10 +1,11 @@
 use chrono::{DateTime, Utc};
 use serde::{Deserialize, Serialize};
+use std::sync::Arc;
 
 #[derive(Serialize, Deserialize, Debug, PartialEq)]
 pub struct ExtensionApiManifest {
     pub name: String,
-    pub version: String,
+    pub version: Arc<str>,
     pub description: Option<String>,
     pub authors: Vec<String>,
     pub repository: String,
@@ -12,11 +13,16 @@ pub struct ExtensionApiManifest {
     pub wasm_api_version: Option<String>,
 }
 
-#[derive(Debug, Serialize, PartialEq)]
+#[derive(Serialize, Deserialize, Debug, PartialEq)]
 pub struct ExtensionMetadata {
-    pub id: String,
+    pub id: Arc<str>,
     #[serde(flatten)]
     pub manifest: ExtensionApiManifest,
     pub published_at: DateTime<Utc>,
     pub download_count: u64,
 }
+
+#[derive(Serialize, Deserialize)]
+pub struct GetExtensionsResponse {
+    pub data: Vec<ExtensionMetadata>,
+}