Fix order of resending messages after restart

The way we build the messages we need to send to approval-distribution
can result in a situation where is we have multiple assignments covered
by a coalesced approval, the messages are sent in this order:

ASSIGNMENT1, APPROVAL, ASSIGNMENT2, because we iterate over each
candidate and add to the queue of messages both the assignment and the
approval for that candidate, and when the approval reaches the
approval-distribution subsystem it won't be imported and gossiped
because one of the assignment for it is not known.

So in a network where a lot of nodes are restarting at the same time we
could end up in a situation where a set of the nodes correctly received
the assignments and approvals before the restart and approve their
blocks and don't trigger their assignments. The other set of nodes
should receive the assignments and approvals after the restart, but
because the approvals never get broacasted anymore because of this bug,
the only way they could approve is if other nodes start broadcasting
their assignments.

I think this bug contribute to the reason the network did not recovered
on `25-11-25 15:55:40` after the restarts.

Signed-off-by: Alexandru Gheorghe <[email protected]>