[Wilds] Shove the logging stuff into a bit of an abstraction before it gets out of control

Summary:
Ref T13098. The logging stuff is starting to get a little sketchy, so wrap it in several layers of class-based indirection before it can escape its cage.

This at least gives us an actual API and structure to work with later instead of scattering a lot of fprintf(STDERR, ....) all over the place.

Test Plan: Ran a few commands, got slightly more sensible/consistent logging out of them.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13098

Differential Revision: https://secure.phabricator.com/D19699