perf(ext/http): optimize set_response for small responses

[marcosc90]

This PR introduces an optimization to set_response to reduce the overhead for responses with a payload size less than 64 bytes. Performance gains are more noticeable when is_request_compressible enters the slow path, ie: -H 'Accept-Encoding: unknown'

Benchmarks

Deno.serve({ port: 3000 }, () => new Response("hello"));

wrk -d 10s --latency -H 'Accept-Encoding: slow' http://127.0.0.1:3000

---

main

Running 10s test @ http://127.0.0.1:3000
  2 threads and 10 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    44.72us   28.12us   3.10ms   97.95%
    Req/Sec   112.73k     8.25k  123.66k    91.09%
  2264092 requests in 10.10s, 308.77MB read
Requests/sec: 224187.08
Transfer/sec:     30.57MB

this PR

Running 10s test @ http://127.0.0.1:3000
  2 threads and 10 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    42.91us   20.57us   2.04ms   97.36%
    Req/Sec   116.61k     7.95k  204.81k    88.56%
  2330970 requests in 10.10s, 317.89MB read
Requests/sec: 230806.32
Transfer/sec:     31.48MB

[mmastrac]

Great win. LGTM