Remove IBC protos in favour of the ibc-proto crate

[romac]

Closes: #458
Closes: #442
Closes: #83

As promised, here is my follow-up to #458 and its corresponding issue in the ibc-proto-rs repository.

Here is the corresponding PR in ibc-proto which removes the generated Cosmos SDK protos and uses them via cosmos-sdk-proto instead: cosmos/ibc-proto-rs#187

Changes

• Remove ibc-go submodule and the corresponding generated proto definitions
• Update Cosmos SDK protos to v0.47.0
• Re-export ICS 23 proto definitions from the ics23 crate instead of bundling them in cosmos-sdk-proto
• Add no-std compatible ProtoJSON (de)serialization to all Protobuf definitions, via Informal's fork of pbjson.

TODO

• Use ics23 v0.11.1 once released (needed for informalsystems-pbjson v0.7.0)
  • PR: chore(rust): Update informalsystems-pbjson to v0.7.0 ics23#274
  • Release PR: chore(rust): Release v0.11.1 ics23#275
• Use tendermint-proto v0.34.1 once released (needed for missing serde annotations on some protos)
  • PR: proto: Add missing serde derives on Protobuf definitions informalsystems/tendermint-rs#1389
  • Release PR: TBD

Questions

• Do we want to update the Cosmos SDK protos further, eg. to v0.50.x?
• What's the best name for the feature guarding the ProtoJSON serialization code? Right now it's serde to match the corresponding feature in ibc-proto, but perhaps pbjson or protojson is a better name?

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This PR is probably best reviewed commit by commit.

@tony-iqlusion This is by no mean the definitive way to go about deduplicating the work, so I am eager to hear what you think about this and to discuss further with you how best to proceeded.

[tony-iqlusion]

@romac seems like you're unblocked on this if you'd like to try to move it forward