Use consistent fake versions for testing deprecations

Problem/Motivation

Drupal\element_info_test\Element\Deprecated:

    @trigger_error(__CLASS__ . ' is deprecated in drupal:10.1.0 and is removed from drupal:11.0.0. See https://www.drupal.org/node/3068104', E_USER_DEPRECATED);

but this class is testing the deprecation system directly and this code should not really be removed in Drupal 11.

Elsewhere we use obviously fake version numbers:

The "deprecated-template.html.twig" template is deprecated in drupal:X.0.0 and is removed from drupal:Y.0.0. Use another template instead. See https://www.example.com

Steps to reproduce

Proposed resolution

Do not use version numbers that could be mistaken for real deprecations; use the fake version numbers in all test cases.

Remaining tasks

Find all cases that need to be updated.
Update them.

User interface changes

API changes

Data model changes

Release notes snippet