Notary native contract

[roman-khimov]

Summary or problem description
Add a new native contract, Notary, with all of the associated logic from #1573 (comment)

Do you have any solution you want to propose?
The GAS locking mechanics of it is rather trivial, verify is a little more complex and it affects the NotaryAssisted attribute a bit as well (dynamic fee).

Target Neo Version

• Neo 3.7

Where in the software does this update applies to?

• Native contracts

Depends on #2896 and #2895. With this implemented C# will be able to process NeoFS sidechains.

[vncoelho]

Did you consider #2646 and #2661?

[roman-khimov]

They have too many things at the same time, some parts from them are already merged (like attributes) and there even were bugs found and fixed during the process. We're going step by step and piece by piece now. In fact, this was the way Notary was implemented in NeoGo way back when, there was no single monstrous PR delivering all of it, we've moved component by component (there is enough of independent parts there).

The main thing is that

With this implemented C# will be able to process NeoFS sidechains.

Even though it still won't be able to process Notary P2P payloads (but that'd be the next step).