Move transfer application and tendermint client to separate crates

[plafer]

We should move the transfer application and the tendermint client to separate crates. This way, these can evolve independently from the core ibc-rs.

Notably, post ibc-rs 1.0, this will mean that if needed we will be able to make breaking changes to the app or client (incrementing the major version) without needing to increment ibc-rs's major version. This will completely decouple core IBC from Tendermint.

[DaviRain-Su]

i can do this.

[plafer]

Thank you! However, let's hold it for now (I should have marked it as blocked). Currently our tests depend on the tendermint client, and we don't want ibc-rs to depend on the future tendermint client crate. And currently, our Mock* types are not test-only; if they were, we could simply import the tendermint client crate as a dev-dependency.

@rnbguy is currently re-architecting our tests (#677), so let's wait until this direction is more clear before we move forward with this issue.