Link directly to the edited section from edit-user-talk events

Adjusted the edit-user-talk event creation to detect and record which section
of the talk page was edited. Flyout, special page, and email messages have
been adjusted to use this section title as a URL fragment when available.

Bug: 46937
Change-Id: I161e2ffda2f2540f64de90cc621fb3b69479d0db
Merge "Link directly to the edited section from edit-user-talk events"