Ref T7447. After compiling inlines which will appear on the changeset, remove inlines which

Later stages remove these anyway, so it doesn't change anything to keep them around, but we can filter them out here cheaply.

This will also let us drive the Differential timeline view with the same logic a few diffs from now, to improve how it renders inlines. Generalize things a little bit.

• Made a comment on the left of diff 1.
• Made diff 2.
• Viewed diff 2 vs diff 1.
• Verified old-left comment was filtered out by the new loop.