Restore old Home mobile menu behavior, hide crumbs

Summary:
Ref T12174.

• Go back to the old mobile behavior (full-screen menu by default, click to see content).
• Hide crumbs from all Home content UIs. I left them on the edit/configure UIs since they feel a little less out-of-place there and some have multiple levels.

Test Plan:
Viewed Home on mobile, viewed /home/ on mobile.

Also, saw no crumbs.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12174

Differential Revision: https://secure.phabricator.com/D17290