Make mobile navigation work properly by default in more cases

Summary:
Fixes T5752. This obsoletes a bunch of old patterns and I'll follow up on those with a big "go do a bunch of mechanical code changes" task. Major goals are:

• Don't load named queries multiple times on search pages.
• Don't require extra code to get standard navigation right on mobile.
• Reduce the amount of boilerplate in ListControllers.
• Reduce the amount of boilerplate around navigation/menus in all controllers.

Specifically, here's what this does:

• The StandardPage is now a smarter/more structured object with setNavigation() and setCrumbs() methods. More rendering decisions are delayed until the last possible moment.
  • It uses this to automatically add crumb actions to the application menu.
  • It uses this to automatically reuse one SearchEngine instead of running queries multiple times.
• The new preferred way to build responses is $this->newPage() (like $this->newDialog()), which has structured methods for adding stuff (setTitle(), etc).
• SearchEngine exposes a new convenience method so you don't have to do all the controller delegation stuff.
• Building menus is generally simpler.

Test Plan:

• Tested paste list, view, edit, comment, raw controllers for functionality, mobile menu, crumbs, navigation menu.
• Edited saved queries.
• Tested Differential, Maniphest (no changes).
• Verified the paste pages don't run any duplicate NamedQuery queries.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T5752

Differential Revision: https://secure.phabricator.com/D14382