Add a linter rule to detect unnecessary semicolons

Summary:
Ref T7409. Adds a rule to detect unnecessary semicolons. The most common scenario I've seen in the wild is the use of semicolons after a class definition:

class MyClass {
  // ...
};

Test Plan: Added unit tests.

Reviewers: Blessed Reviewers, epriestley

Reviewed By: Blessed Reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7409

Differential Revision: https://secure.phabricator.com/D12139