Add info about reverse_proxy on status page

This issue is a bit more critical since https://www.drupal.org/sa-core-2023-004: → the phpinfo page doesn't display anymore the request headers.
The status page should return the following order HTTP headers in order to setup or debug the reverse proxy settings : REMOTE_ADDR, HTTP_X_FORWARDED_*, HTTP_HOST, SERVER_PORT, REQUEST_SCHEME.

Here's a first shot, still missing:

• wording, spell cheking, grammar
• unit test ?
• Analysis of the forwarded header's "for" attributes
• Adding a card on status page with current detected scheme, host, port and remote address

The Needs Review Queue Bot → tested this issue. It fails the Drupal core commit checks. Therefore, this issue status is now "Needs work".

This does not mean that the patch necessarily needs to be re-rolled or the MR rebased. Read the Issue Summary, the issue tags and the latest discussion here to determine what needs to be done.

Consult the Drupal Contributor Guide → to find step-by-step guides for working with issues.

The Needs Review Queue Bot → tested this issue. It fails the Drupal core commit checks. Therefore, this issue status is now "Needs work".

This does not mean that the patch necessarily needs to be re-rolled or the MR rebased. Read the Issue Summary, the issue tags and the latest discussion here to determine what needs to be done.

Consult the Drupal Contributor Guide → to find step-by-step guides for working with issues.

I agree this could be useful, it is sometimes hard to debug reverse proxy problems in production.
But I feel like the MR is trying to do too many different things and adds a lot of information. I'm not sure everything is relevant to everyone and it will make the MR harder to review.
Displaying the host, IP address, protocol and port detected by Drupal (using the methods on the Request object) would be a great start.

Also this will need tests.

To be clear this MR does :

• Add an "info block" that display the basic request info as viewed by drupal/symfony : scheme,host,port and client ip
• Add "requirements lines":
• httpS status
• Detected scheme, host & port
• Detected remote client IP
• Reverse proxy info with $settings['reverse_proxy'] status and some details to help its setup (headers)
• Add a warning if https is not detected
• Add a warning if any "forwarded" header is present but $settings['reverse_proxy'] is not enabled

Remaining tasks:

• Add tests
• Rephrase/reword messages to make them clearer