|pump and |sink call into each other in three places
related to nacks and naxplanations (sending a nack,
notifying the |pump of a naxplanation, or dropping a
nack from the |sink). This intra calls are making implicit
updates to more parts of the state than the core should
manage. To avoid that we emit a move to %arvo, encoded
as an %ames plea, to handle that in the next event.
previously we were acking the nack-trace message (adding a %send move)
before notifying the message-pump with a %near task. Now, due to the
refactoring we invert the order of those moves. This seems safe but will
determine with livenet testing
Including these in pkg/arvo has caused many minor problems over the
years. We don't want to include them in releases, but this often meant
excluding them manually, which was error-prone.
Here, we move them out of /pkg/arvo/tests and into /tests. CI will have
to be updated to match, since we'll still want to include tests there.
