Change default chunk size from 4Kb to 64Kb

[Kludex]

• Closes Make FileResponse.chunk_size variable #1100

@tomchristie On that issue, you said that "httpx uses 64k read size", but I couldn't find that. Do you mind pointing me out what did you mean?

[dalf]

The related issue in httpcore : encode/httpcore#135
In the source code: https://github.com/encode/httpcore/blob/4f6d793e440ffeda31d7d064b434ad8083d42634/httpcore/_async/http11.py#L38

[Kludex]

Thanks @dalf ! Much appreciated! 🎉

[florimondmanca]

Looking good! That's quite a similar change to the one we made in HTTPX indeed, and for the same reason (improving transfer speed by using larger chunks).

[Kludex]

Thanks @florimondmanca ! 🎉