Add title to ObjectItemList headers for truncated displays

Summary: Ref T6723. This allows you to hover over truncated headers and get the full text if needed.

Test Plan:
Hover over header, see full title

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T6723

Differential Revision: https://secure.phabricator.com/D10958