Treat unreleased hardforks in a special way #3719
Description
Is your feature request related to a problem? Please describe.
I'm always frustrated when tests fail in nspcc-dev/neofs-node#3040. Turns out, we need nspcc-dev/neofs-testcases#903 for them to work at all, otherwise some internal logic easily breaks with
Error: can't create N3 client: failed to get network magic: unexpected hardfork: Echidna
which is kinda expected if it's an official HF. But this case is a bit more special, it's not yet finalized hardfork.
Describe the solution you'd like
We can not enable the latest hardfork by default if it's not yet released. It'll require some tweaking for sure, but it can make upgrades easier to handle. The idea is that we can introduce hardfork names earlier than we introduce proper hardfork support, so after an upgrade to newer NeoGo that has new HF definition upgrading to the subsequent version where it's finalized will go smoother, nothing will break immediately.
Describe alternatives you've considered
Leaving as is, it's fair as well, the latest and greatest known is Echidna at the moment, so it's enabled by default for private networks. Good for testing as well, that's the behavior you likely expect in NeoGo proper.