perf(ext/streams): optimize async iterator (#20541)

This PR optimizes `ReadableStream` async iterator

### Benchmarks

```js
Deno.bench("Stream - iterator", async () => {
  const stream = new ReadableStream({
    start(controller) {
      controller.enqueue(new Uint8Array([97]));
      controller.enqueue(new Uint8Array([97]));
      controller.close();
    },
  });

  for await (const chunk of stream) {}
});
```

**main**

`2 chunks`
```
cpu: 13th Gen Intel(R) Core(TM) i9-13900H
runtime: deno 1.36.4 (x86_64-unknown-linux-gnu)

benchmark              time (avg)        iter/s             (min … max)       p75       p99      p995
----------------------------------------------------------------------- -----------------------------
Stream - iterator      12.45 µs/iter      80,295.5   (10.5 µs … 281.12 µs)  12.13 µs  26.71 µs  33.63 µs
```
`20 chunks`

```
benchmark              time (avg)        iter/s             (min … max)       p75       p99      p995
----------------------------------------------------------------------- -----------------------------
Stream - iterator      32.99 µs/iter      30,312.2    (28.13 µs … 1.21 ms)   31.8 µs  81.82 µs 179.93 µs
```
---

**this PR**

`2 chunks`
```
cpu: 13th Gen Intel(R) Core(TM) i9-13900H
runtime: deno 1.36.4 (x86_64-unknown-linux-gnu)

benchmark              time (avg)        iter/s             (min … max)       p75       p99      p995
----------------------------------------------------------------------- -----------------------------
Stream - iterator       9.37 µs/iter     106,700.8   (8.35 µs … 730.71 µs)   9.15 µs  13.12 µs  18.17 µs
```
`20 chunks`
```
benchmark              time (avg)        iter/s             (min … max)       p75       p99      p995
----------------------------------------------------------------------- -----------------------------
Stream - iterator      16.59 µs/iter      60,270.0    (12.08 µs … 1.37 ms)  15.06 µs  83.03 µs 123.52 µs
```

0 files changed, 0 insertions, 0 deletions