Log response length for rails and API requests

What does this MR do and why?

Log response length for rails web and API requests. This allows us to correlate response length against request performance.

The work is behind a feature flag for protection.

Code based off https://github.com/rack/rack/blob/main/lib/rack/content_length.rb.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Closes #366618 (closed)