Allow headers size extend to maxRequestHeadersSize in http client

[shaoxt]

PR for #12436

[sbordet]

@shaoxt make sure you comply with the Eclipse ECA, see https://github.com/jetty/jetty.project/blob/jetty-12.0.x/CONTRIBUTING.md, otherwise we cannot accept this contribution.

[shaoxt]

[shaoxt]

Had PR merged before. And resigned the ECA again.

@shaoxt make sure you comply with the Eclipse ECA, see https://github.com/jetty/jetty.project/blob/jetty-12.0.x/CONTRIBUTING.md, otherwise we cannot accept this contribution.

[joakime]

Your various commits on this PR have 3 different email addresses associated with it.

Example:

• https://github.com/jetty/jetty.project/commit/6306d175d499c0c5f9715cc6989fc032f882b608.patch - gmail address
• https://github.com/jetty/jetty.project/commit/d49a07a27c337743d91b36c18cc3843046dfa1bc.patch - intuit address

Squash (or rebase) all of these commits and make it a single commit with just your registered gmail address.

[shaoxt]

Close this PR for the invalid authors.