http: make early hints implementation more generic

[mcollina]

In #44180, we thought that the "early hints" implementation is not complete as it landed.

We need to fix it either as:

response.writeEarlyHints({
  link: 'your link header',
  x-trace-id: 'id for diagnostics'
})

or

response.writeInfomation(103, "Early Hints", {
  link: 'your link header',
  x-trace-id: 'id for diagnostics'
})

[anonrig]

I'm working on this task, and will open a pull request soon.

[anonrig]

Can a link header be a string and an array just like the parameter type of response.writeEarlyHints?

For example should both of them be valid?

response.writeEarlyHints({
  link: ['</styles.css>; rel=preload; as=style']
})

response.writeEarlyHints({
  link: '</styles.css>; rel=preload; as=style'
})

[mcollina]

Yes