Add ViewController and SearchEngine for SSH Public Keys

Summary:
Ref T10917. This primarily prepares these for transactions by giving us a place to:

• review old deactivated keys; and
• review changes to keys.

Future changes will add transactions and a timeline so key changes are recorded exhaustively and can be more easily audited.

Test Plan:

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10917

Differential Revision: https://secure.phabricator.com/D15946