Added SavedChangesMessage instance and updated spec to use mock data

What does this MR do?

This MR ensures the SavedChangesMessage component actually renders when a valid edit has occurred. Otherwise the assumed view state is interpreted as the skeleton loader or the edit UI itself.

In the next milestone we will leverage a router to better manage the parent page/screen views.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

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