feat(ext/http): abort event when request is cancelled (#26781)

```js
Deno.serve(async (req) => {
  const { promise, resolve } = Promise.withResolvers<void>();

  req.signal.addEventListener("abort", () => {
    resolve();
  });

  await promise;

  return new Response("Ok");
});
```

1 files changed, 9 insertions, 4 deletions

diff --git a/ext/http/00_serve.ts b/ext/http/00_serve.ts
index 8cfd7ad53..7bf83e49c 100644
--- a/ext/http/00_serve.ts
+++ b/ext/http/00_serve.ts
@@ -11,10 +11,10 @@ import {
   op_http_cancel,
   op_http_close,
   op_http_close_after_finish,
-  op_http_get_request_cancelled,
   op_http_get_request_headers,
   op_http_get_request_method_and_url,
   op_http_read_request_body,
+  op_http_request_on_cancel,
   op_http_serve,
   op_http_serve_on,
   op_http_set_promise_complete,
@@ -375,11 +375,16 @@ class InnerRequest {
     return this.#external;
   }
 
-  get isCancelled() {
+  onCancel(callback) {
     if (this.#external === null) {
-      return true;
+      callback();
+      return;
     }
-    return op_http_get_request_cancelled(this.#external);
+
+    PromisePrototypeThen(
+      op_http_request_on_cancel(this.#external),
+      callback,
+    );
   }
 }