Render historic comments for files, inline

[kumar303]

Describe the problem and steps to reproduce it:

Consider this imaginary UI flow:

• Sign in as a reviewer
• Open a version compare page (or browse page)
• Before entering comments, try to look at a previous version to see what comments were left last time
• Begin entering comments for the new version

What happened?

n/a

What did you expect to happen?

The older comments should be displayed when viewing an already reviewed version

Anything else we should know?

This depends on https://github.com/mozilla/addons/issues/6647

This is similar to viewing draft comments: https://github.com/mozilla/addons-code-manager/issues/713

┆Issue is synchronized with this Jira Task

[EnTeQuAk]

With mozilla/addons#6647 being fixed, I'm going to remove the needs: api label for now. Let me know if you need anything specific on top of that.

[kumar303]

We do have an API to list comments but I think it needs some tweaks to support this issue. See https://github.com/mozilla/addons/issues/7118