Modernize DifferentialInlineCommentQuery

Summary:
Ref T7447. This class is currently a big mess with a lot of withWeirdSpecialThingUsedInOnePlace() type qualifiers.

Try to generalize/normalize it a bit.

Test Plan:

• Viewed inline comments.
• Created a new inline comment.
• Edited an inline comment.
• Marked an inline comment complete.
• Deleted, then undeleted an inline comment.
• Previewed inline comments.
• Viewed drafts as another user, verified they don't show up.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: yelirekim, epriestley

Maniphest Tasks: T7447

Differential Revision: https://secure.phabricator.com/D12483