Add active trail information via the Decoupled Router

Problem/Motivation

Active trail information is required for Decoupled Menu usage.

Steps to reproduce

Proposed resolution

Add active menu trail information to the Decoupled Router response.
Maybe using a PathTranslatorSubscriber or similar to attach the data to the Decoupled Router, or may require changes to the Decoupled Router.
An example of a PathTranslatorSubscriber: https://git.drupalcode.org/project/druxt/-/blob/0.0.x/src/EventSubscribe...

Remaining tasks

Do the thing.

User interface changes

API changes

Data model changes