feat: add destroy() to types and releated unit tests

Author: AllanZhengYP

packages/types/src/client.ts

@@ -46,6 +46,8 @@ interface InvokeFunction<
 
 /**
  * A general interface for service clients, idempotent to browser or node clients
+ * This type corresponds to SmithyClient(https://github.com/aws/aws-sdk-js-v3/blob/master/packages/smithy-client/src/client.ts).
+ * It's provided for using without importing the SmithyClient class.
  */
 export interface Client<
   Input extends object,
@@ -55,4 +57,5 @@ export interface Client<
   readonly config: ResolvedClientConfiguration;
   middlewareStack: MiddlewareStack<Input, Output>;
   send: InvokeFunction<Input, Output, ResolvedClientConfiguration>;
+  destroy: () => void;
 }

packages/util-create-request/src/foo.fixture.ts

@@ -36,7 +36,8 @@ export const fooClient: Client<any, InputTypesUnion, OutputTypesUnion, any> = {
       this.middlewareStack,
       this.config,
       undefined
-    )({ input })
+    )({ input }),
+  destroy: () => {}
 };
 
 export const operationCommand: Command<