feat: As a User, I want to add delayed_body_filter so that run tracing code both in the first and in the last

[spacewander]

Issue description

As the discussion in #6500, we need to run the tracing plugins both in the front of request processing and at the end of response body processing.

One of the solutions is to add a delayed_body_filter phase, so the plugins can be run in the first of the delayed_body_filter and also the last of the body_filter.

[tzssangglass]

SGTM