R1:500506bfef28

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. {icon bomb}
- Daemons process mail with empty `excludePHIDs` list.

Store it in the persistent properties array instead.

Also remove the "override self…