Make FileFinder's withName() + withSuffix() work like every other Query class

Summary:
See PHI336. See https://discourse.phabricator-community.org/t/using-the-filefinder-class-withsuffix-and-withname-return-entries-with-either-the-suffix-or-the-name-match/1035?u=dangerouslyil.

Currently, withName() and withSuffix() mean "with either the name or the suffix", which isn't how any other Query class works.

Note that "name" means "exact name", per find semantics, so this combination isn't necesarily terribly useful. However, the current behavior is clearly surprising given that everything else in the project works differently.

Test Plan: Added a test case for both constraints, made it pass.

Reviewers: amckinley

Reviewed By: amckinley

Subscribers: yelirekim

Differential Revision: https://secure.phabricator.com/D18979