Hot reloading of traces run into streaming issues on some browsers

### Issue Identified
When utilising the recommended debug loop of importing traces onto https://ui.perfetto.dev/ I noticed that doing so via the webUI provided by `watch_trace.html` by running `python watch_trace.py` actually throws `BrokenPipeError: [Errno 32] Broken pipe` when `/trace.json` is fetched via `await fetch(traceUrl);`.

### Steps to reproduce
Issue reproduced on Chrome Version 143.0.7499.193

1. Execute `python perf_takehome.py Tests.test_kernel_trace` to generate a local `trace.json`
2. Run `python watch_trace.py` and wait for a tab of `http://localhost:8000/` to open
3. Select `/trace.json` and press "Open Perfetto"
4. Perfetto tab will not open, and `BrokenPipeError: [Errno 32] Broken pipe` error should appear in your python terminal

### Solution proposal
Investigating further, when calling `/trace.json` directly in the browser actually works fine, when checking the Javascript code responsible for this we see that blob is populated via
```
const resp = await fetch(traceUrl);
const blob = await resp.blob();
```
This raises issues in some browsers as our absence of a Content-Length header (which is fine for streaming) is actually causing the browser to abort the stream if the `/trace.json` is big enough.

To fix this for those browsers, the fetching logic in Javascript can be modified to populate chunks with a reader as they come and then populated into a chunk manually.

```
const resp = await fetch(traceUrl);
const reader = resp.body.getReader();
const chunks = [];

while (true) {
const { done, value } = await reader.read();
if (done) break;
chunks.push(value);
}
const blob = new Blob(chunks);
```
Applying this change allows the request to succeed when called within the Javascript in the tab served by `python watch_trace.py`