Add DiffusionBranchListView for browsing branches

Summary: Adds a new DiffusionBranchListView which replaces the BranchTable when browsing all branches in Diffusion. Has all the same capabilities, but is easier to read, adds a Compare button, and plays nicely on mobile. It does take up more space, but I think that's generally OK here since we expect our branches to not be heaping piles of intern revert branches.

Test Plan:
Follow a few repositories with branches, like Phabricator and KDE's Krita. View layouts on mobile, tablet, desktop. Try out new compare button.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: avivey, Korvin

Maniphest Tasks: T12824

Differential Revision: https://secure.phabricator.com/D18113