Persist excluded recipients when saving mail

Summary:
Fixes T5185. The fundamental issue is that this excludePHIDs property was not saved, so the logic went like this:

• Generate excludePHIDs correctly.
• Pass excludePHIDs through the stack.
• Perform some other computations correctly.
• Queue the mail for the daemons, throwing it away.
• Daemons process mail with empty excludePHIDs list.

Store it in the persistent properties array instead.

Also remove the "override self mail" thing, since it's only used by bin/mail send-test and suffers from the same issue. I think it's too useless to fix, since even if you get caught by it, bin/mail makes it clear why the message was dropped.

Test Plan:
Notable:

• exclude present in properties
• Exclusion reason under RECIPIENTS header

{P1229}

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T5185

Differential Revision: https://secure.phabricator.com/D10234