Stabilize tcp_quickack

[devnexen]

to stabilise the quickack part for now, tcp_deferaccept had been added at a later stage.

The related API calls are the following

// std::os::linux::net

// sealed trait, implemented for std::net::TcpStream
pub trait TcpStreamExt: Sealed{
  fn quickack(&self) -> io::Result<bool>;
  fn set_quickack(&self, quickack: bool) -> io::Result<()>;
}

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[ChrisDenton]

This needs a stabilization fcp

r? libs-api

[tgross35]

@devnexen could you add an API summary to the top post? Like #129401

[devnexen]

done.