Record account recovery email links in the user activity log and make the mail message reference the log

Summary:
Depends on D20672. Ref T13343. When a user requests an account access link via email:

• log it in the activity log; and
• reference the log in the mail.

This makes it easier to ban users misusing the feature, provided they're coming from a single remote address, and takes a few steps down the pathway toward a button in the mail that users can click to report the action, suspend account recovery for their account, etc.

Test Plan:

• Requested an email recovery link.
• Saw request appear in the user activity log.
• Saw a reference to the log entry in the mail footer.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13343

Differential Revision: https://secure.phabricator.com/D20673