UpdateSemverContribTest incorrectly sets core version

Problem/Motivation

In UpdateSemverContribTest::setProjectInstalledVersion(), we do this to set the installed version of Drupal core:

      'drupal' => [
        'project' => 'drupal',
        'version' => '8.0.0',
        'hidden' => FALSE,
      ],

This does not match the logic in update_test_system_info_alter(), which expects an #all key to set the core version (as seen in UpdateSemverCoreTest::setProjectInstalledVersion()).

So basically UpdateSemverContribTest is wrong here, and possibly passing falsely.

Steps to reproduce

N/A

Proposed resolution

Use the #all key to change the core version in UpdateSemverContribTest.

Remaining tasks

Post a test-only merge request which makes the change, just to see if any tests break, and which ones.

If no tests break, it means our coverage is lacking and we need to add some. If tests do break, fix them. This is what should be done in the second merge request.

User interface changes

None.

API changes

None.

Data model changes

None.

Release notes snippet

None.