WIP: Jdb/refactor diff table views

What does this MR do?

This MR is the first in a series of refactors to prepare for better UX with multiline comments. It decouples the presentational logic that ties a lot of the inner workings to HTML tables.

Screenshots

n/a

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Code review guidelines
• Merge request performance guidelines
• Style guides

Availability and Testing

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