Allow headers size extend to maxRequestHeadersSize in http client

[shaoxt]

Fixes #12436

Allow headers size extend to maxRequestHeadersSize in http client

[sbordet]

Can you please:

1. Apply the review comments.
2. Rebase these changes against branch jetty-12.1.x, and squash them in just 1 commit.
3. Move the tests to HttpClientTest and actually call setMaxRequestHeadersSize() in the test so that we will test it is working.

I am probably make your changes part of a larger set of changes that improve the behavior of the current implementation.

Thanks!

[shaoxt]

Thanks for reviewing the PR. Created a new PR for required changes
#12499
For some reasons, the last commits I tried to squash them in 1 commit. but git said the commits from two different parents.

Can you please:

1. Apply the review comments.
2. Rebase these changes against branch jetty-12.1.x, and squash them in just 1 commit.
3. Move the tests to HttpClientTest and actually call setMaxRequestHeadersSize() in the test so that we will test it is working.

I am probably make your changes part of a larger set of changes that improve the behavior of the current implementation.

Thanks!