Add id to chat request (#243239)

* Add id to chat request

* Support proposed api check

* Do some casting

src/vscode-dts/vscode.proposed.chatParticipantPrivate.d.ts

@@ -50,6 +50,10 @@ declare module 'vscode' {
 	}
 
 	export interface ChatRequest {
+		/**
+		 * The id of the chat request. Used to identity an interaction with any of the chat surfaces.
+		 */
+		readonly id: string;
 		/**
 		 * The attempt number of the request. The first request has attempt number 0.
 		 */