netty/jetty: review performance degradation on 4.x

[jknack]

On 4.x There is a difference of 3000000 less compared to Netty. While 3.x where very closed to raw Netty.

There is another Netty tests but that one is running on loom, which isn't supported by Jooby today.

It is similar for Jetty

3.x results: https://www.techempower.com/benchmarks/#section=test&runid=aa3d7016-7864-421f-a8ba-28f8feacb339&l=zhuqrj-cn3&test=plaintext

4.x results https://www.techempower.com/benchmarks/#section=test&runid=e8b36ecc-d623-48bb-936d-d043e9db2c13&l=zhuqrj-cn3&test=plaintext