Implement RPC session iterator extensions

[AnnaShaleva]

Implement neo-project/neo#3429. Keep in mind that:

• It should be an RPC server extension, move it under some SessionExpansionExtension and ensure that compatibility is preserved with C# nodes and old NeoGo servers.
• Extend getversion response with this setting.
• Ensure RPC client and unwrap package can work with both SessionExpansionExtension enabled and disabled.
• Make sure Invoker can handle it properly.

[roman-khimov]

Most likely we'll need to release a version, upgrade all clients and only then enable it in production, because obviously current clients can be confused upon receiving expanded iterator with session data.