Resolve "Lines changed statistics is not easily visible in MR changes view"

What does this MR do?

Displays line change statistics in MRs for the entire MR as well as per file

(i.e. files changed, lines added and lines removed)

What are the relevant issue numbers?

Closes #52347 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the style guides