Add mounts data to apollo cache

What does this MR do?

Add mounts data property to the apollo cache in preparation for using the mounts data to display images with relative URLs.

Note: This is the 1st iteration towards delivering #218531 (closed)

Screenshots

No visual changes are expected

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

Issue #218531 (closed)