perf(ext/http): increase buffer size to 64kb

[marcosc90]

Towards #13608

The current buffer size is the bottleneck. This PR increases the buffer size to 64kb, even if the largest possible size for a TLS packet is 16 * 1024 + 256, we're reading at a slower rate than the upload speed, so packets are being buffered,

deno/ext/http/lib.rs

Line 851 in e2828ad

let len = min(buf.len(), chunk.len());

You can check that chunk.len() is usually greater than the max TLS packet size.

The higher the buffer size the faster it'll be, 64kb seems like a reasonable default value.

On my computer, streaming a 2gb upload to disk, takes 2.4s with this update down from 4.5s.

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Adding a bufSize/highWaterMark option to Deno.serveHttp or httpConn.nextRequest() to change the default value would be a good next step.

[littledivy]

LGTM!

[marcosc90]

Since we started working towards FastStreams this code path no longer exists. Change implemented in #16096