Improve declaration formatting linter rule for anonymous functions

Summary: Ref T8742. Anonymous functions should have a space after the function keyword. Additionally, ensure that there is a space before and after the use token.

Test Plan: Modified existing test cases.

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: Korvin

Maniphest Tasks: T8742

Differential Revision: https://secure.phabricator.com/D13804