d5a9af5860 is incompatible with the NeoFS
mainnet sidechain, so we add the old logic to the pre-Aspidochelone
behaviour. Changing flags at newMethodAndPrice() is a bit less convenient
unfortunately because this will affect interop validity checks, so let's have
this kludge here.
And include some node-specific configurations there with backwards
compatibility. Note that in the future we'll remove Ledger's
fields from the ProtocolConfiguration and it'll be possible to access them in
Blockchain directly (not via .Ledger).
The other option tried was using two configuration types separately, but that
incurs more changes to the codebase, single structure that behaves almost like
the old one is better for backwards compatibility.
Fixes#2676.
