Move Pholio to SearchFields

Summary:
Ref T8441. Ref T7715.

• Update PholioSearchEngine.
• Automatically add project fields.
• Update Paste to support project search.
• Simplify common Query class construction.

Test Plan:

• Searched for pastes.
• Searched for mocks.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T7715, T8441

Differential Revision: https://secure.phabricator.com/D13174