Move the "select a line range" inline code to DiffInline
Summary: Ref T12616. This makes line range selection use the new code, and removes the remainder of the old "hover a line number" / "select a line range" code.
Test Plan: Hovered line numbers; selected line ranges.
Reviewed By: chad
Maniphest Tasks: T12616
Differential Revision: https://secure.phabricator.com/D17927