Give user log types a tokenizer and datasource instead of a page of checkboxes

Summary: Depends on D20671. Ref T13343. Now that log types are modular, provide a datasource/tokenizer for selecting them since we already have a lot (even after I purged a few in D20670) and I'm planning to add at least one more ("Request password reset").

Test Plan:

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13343

Differential Revision: https://secure.phabricator.com/D20672