We currently have an PhabricatorSearchIntField , but it doesn't do what you'd expect, and hardly used anywhere - see disussion in D25479.

1. Look around for other things that might act like int field - like CustomIntField?
2. How come we never needed a working int input? we probably have at least some places where we expect a user to enter a number, right?
3. maybe fix the PhabricatorSearchIntField to do what it names implies.