Add a config to disable jQuery and CSS animations

What does this MR do?

Adds a config to disable CSS and jQuery animations. This will be used by the e2e QA tests by setting the omnibus config gitlab_rails['gitlab_disable_animations'] = true;.

Related issue: #43663 (closed)

Requried for: gitlab-qa!360 (merged)

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers