Since it's a bit weird having service specific implementation details
inside the general service `._daemon` mod, and since i'd mentioned
trying this re-org; let's do it B)
Requires enabling the new mod in both `pikerd` and `brokerd` and
obviously a bit more runtime-loading of the service modules in the
`brokerd` service eps to avoid import cycles.
Also moved `_setup_persistent_brokerd()` into the new mod since the
naming would place it there even though the implementation really
wouldn't (longer run) since we want to split up `.data.feed` layer
backend-invoked eps into a separate actor eventually from the "actual"
`brokerd` which will be the actor running **only** the trade control eps
(eg. trades_dialogue()` and friends).
0b43e0aa8c