[Redesign] Update Inline Comment UI
Summary: Ref T8099, Simplifies the button bar with a borderless option and implements in Differential Inline Commenting.
Test Plan:
Review new and old comments, submitted, unsubmitted, ghosts, done.
{F562765}
Reviewers: btrahan, epriestley
Reviewed By: epriestley
Subscribers: epriestley, Korvin
Maniphest Tasks: T8099
Differential Revision: https://secure.phabricator.com/D13475