Fix documenation URLs that are 404, part 1

Problem/Motivation

There are documentation URLs in core that are 404. This is to fix what should be the easiest ones.

Steps to reproduce

Proposed resolution

1. https://www.drupal.org/node/3425340 →
2. https://www.drupal.org/node/3508905 →
3. https://www.drupal.org/node/3518065 →
4. https://www.drupal.org/project/drupal/issues/3550627 →
5. https://www.drupal.org/docs/8/core/modules/package-manager →
6. https://www.drupal.org/documentation/modules/mysqli →
7. https://www.drupal.org/node/add/project-issue/auto_updates →
8. https://www.drupal.org/project/auto_updates/issues/3312619#comment-14801308 📌 Ensure all validation results use translatable strings except when created from throwables Fixed
9. https://www.drupal.org/project/auto_updates/issues/3338651 📌 Drupal core's coding standards forbid translated exceptions, but does that anyway — f.e. FileValidationException Active

Remaining tasks

Review
Commit

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet