[Do not merge] ADR-8 vertical spike

[alpe]

Spike to discuss a concrete example.
This includes a some of hacks to make it work without modifying wasmvm.

A good start would be to look at TestIBCAdr8WithTransfer for the test scenario. Ics29 fees or edge cases are not covered
The middleware integration is done in app.go

For the callback to the contracts, 2 new methods are added to the wasmvm interface and mocked for proof of concept

• OnIBCPacketAcked
• OnIBCPacketTimedOut

For the callback registration a custom message was added that the reflect contract emits in the test:

type RegisterPacketProcessedCallback struct {
	// Sequence is the ibc packet sequence number
	Sequence            uint64 `json:"sequence"`
	ChannelID           string `json:"channel_id"`
	PortID              string `json:"port_id"`
	MaxCallbackGasLimit uint64 `json:"max_callback_gas_limit"`
}

The message is handled in the XMessageHandler and contains some ugly hack for the reflect contract.

Authorization

• on callback registration, it is checked that the actor is a contract
• on ack/timeout handling, the packet sender is only accepted for a registered hook

New Packages

• xwasmvm are extensions to WasmVm for the spike only. If they make sense, then they should be moved upstream
• xadr8 are common parts that are not CosmWasm specific. If they make sense, they could be living in ibc-go for example

[alpe]

This is unused

[alpe]

requires PortID as well

[alpe]

In case somebody reads the article by the IBC team which goes in some different direction. This spike was built for them to demo the integration and callback registration. There were also a call and long discussions on internal slack.
This is an important feature for the community. We need to discuss internally how to proceed, now.