Add support for the diff module to the src/Plugin/Field/FieldFormatter/ContentBlockTitleReplacementFormatter.php

Problem/Motivation

The diff module allows to display changes across revisions, and optionally allows it visually. In that situation the ContentBlockTitleReplacementFormatter won't match with any of the supported routes and will display the default text "Placeholder for replacement title"

Steps to reproduce

- Install the diff module
- Configure the diff module to display the layout "Visual inline"
- Create a node from a content type supporting revisions and layout builder (a page for example)
- Go to layout builder and do some changes
- Go to layout builder and do some changes again
- Go to the revisions tab
- Click on "Compare selected revisions" button

Proposed resolution

- Add a new condition to the switch case at \Drupal\rocketship_core\Plugin\Field\FieldFormatter\ContentBlockTitleReplacementFormatter::viewElements to support the diff.revisions_diff route

Remaining tasks

- Create a patch
- Review
- Test

User interface changes

- None

API changes

- None

Data model changes

- None