Refactor suggestions regarding relay modules

[hackfisher]

1. EthereumRelay implements EthereumRelayabe
2. Dispatch calls are all put into EthereumRelay, relay_header(EthereumHeaderThing). The parameter EthereumHeaderThing uses EthereumRelayabe codec into vec and is passed to RelayerGame’s submit_proposals. When using it, adjust the EthereumRelayabe interface. In this way, both apps and explorer can easily analyze the EthereumHeaderThing Type
3. As a more general and closed module, RelayerGame can manage its own storage, events and on_initialize/on_finalize, which are related to verifying the game sub-protocol.
4. EthereumRelay Dispatch Call calls RelayerGame to complete tasks related to verifying game sub-protocols.

[hackfisher]

ConfirmBlockManagementError should be a Error, not a event.

[aurexav]

Currently, the implementation is ugly, very inefficiency.

Relay encode the header things pass to Game, then Game call Relay to decode them. Such as verify_raw_header_thing, verify_raw_header_things are unnecessary under this architecture.

We should eventually separate the APIs. Refactor the Game's protocol.

Is possible to make Game an actual protocol? Like phragmen which defined in primitives.

[clearloop]

It might be a solution to implement a struct named Relayable:

struct Relayable {}

struct EthereumHeaderThing {}
struct TronHeaderThing{}

impl Into<Relayable> for EthereumHeaderThing{}
impl Into<Relayable> for TronHeaderThing{}

Or use a trait and proc_macro

struct Relayable {
  header: String,
  mmr: H256,
}

trait RelayableTrait {
   fn relayable() -> Relayable
}

/// -snippet-
/// a proc macro

#[derive(Relayable)]
struct EthHeaderThing{}

#[derive(Relayable)]
struct TronHeaderThing{}

[hackfisher]

Currently, the implementation is ugly, very inefficiency.

Relay encode the header things pass to Game, then Game call Relay to decode them. Such as verify_raw_header_thing, verify_raw_header_things are unnecessary under this architecture.

We should eventually separate the APIs. Refactor the Game's protocol.

Is possible to make Game an actual protocol? Like phragmen which defined in primitives.

Can we remove RawHeaderThing and make HeaderThing an associate type for both Relay and RelayerGame?

Then for EthereumRelay, we can assign EthereumHeaderThing to this associate type, for TronRelay, we can assign TronHeaderThing.

We will not need encode/decode process between them then.

Currently RelayerGame has chain storages, it's more like a pallet than a primitives library.