Shared active set

[mathcrypto]

As a result of the abnormal growth in the number of ATXs, the sync process isn’t as effective as it should be. It does not guarantee that node will download all missing ATXs which then causes poor ATX propagation. As a result, many nodes are using slightly different active sets.

In order to guarantee that most nodes are using the same active set, we have implemented a short term solution which
includes sharing an active set from our server that nodes use as a base (they can add any additional ATXs they know
about). The long term solution would be to encode the active set with a difference, rather than re-encoding whole activeset spacemeshos/go-spacemesh#5282. and additionally we may consider building active deterministically from 1 or several blocks, spacemeshos/go-spacemesh#5288. This may not be an issue at all if sync and gossip are improved and work as intended.

See spacemeshos/go-spacemesh#5366