Update ICS-4 to pass relayer/signed to modules

[ethanfrey]

This changes the ibc handler code, but no changes to the packets send over the wire, so non-breaking on the protocol layer.

It provides some needed information to allow fee incentivization for IBC packets, both in the ics20-2 proposal #577 as well as the more general relayer fee proposal #578

[cwgoes]

Concept ACK, this seems straightforward.

Just a quick ping @colin-axner - any difficulties here from the ibc-go angle (presumably not)?

[colin-axner]

Just a quick ping @colin-axner - any difficulties here from the ibc-go angle (presumably not)?

Nope, @ethanfrey has already kindly implemented the changes

TimeoutOnClose needs to be updated in this pr though

[ethanfrey]

TimeoutOnClose needs to be updated in this pr though

There was also the idea to expose this info for the various channel lifetimes and such, but I would request that in another PR as I see it as a different but related PR.

TimeoutOnClose seems to be more packet-related however and I will add that

[AdityaSripal]

concept ACK

Will this PR include wrapping the relayer address in the ack or will this be in a future PR?

[ethanfrey]

Will this PR include wrapping the relayer address in the ack or will this be in a future PR?

That is a future and more contraversial point. I am trying to do step by step where I understand there to be consensus already

[ethanfrey]

What do I need to get this merged? It has 2/3 approvals and support on the IBC call.

I am happy for more review, but I would like to see a bit faster feedback cycle if there are no objections.
That would let me to build a series of small, easy to review PRs on top of each other.
Otherwise, you just encourage mega-PRs.

In particular, I want to make a PR on acknoweldgement format that should build on this.

[ethanfrey]

@milosevic I guess this just needs your review