Re-split sov-ibc and sov-ibc-transfer modules, and also separate test utils into sov-ibc-mocks

[Farhad-Shabani]

Background

As of informalsystems/sovereign-sdk#11, sov-ibc and sov-ibc-transfer have been combined.
This decision was made because sov-ibc is implemented in a way that it couldn't function independently without sov-ibc-transfer. Additionally, not clear how a new IBC application should be plugged in without needing to hardcode things, at least not in the Ibc<C, Da> struct. Consequently, this led to confusion that these two components should coexist.

However, recent experience of working on the demo-rollup revealed:

In the context of the rollup application, each of the structs implemented ModuleInfo represents a distinct module within the Sovereign SDK system. Thus, each should essentially be plugged in, initialized, and ideally operated independently. Thus, The mentioned merge hasn't offered much in practice. Conversely, that has complicated dependency and feature management. We may want to enable a feature in one module without necessarily activating it for the entire repository.

To decouple sov-ibc and sov-ibc-transfer and clear up mentioned confusion, the issue #13 has been opened.

Proposal

Within this issue, we aim to re-split sov-ibc and sov-ibc-transfer with some adjustments from demo-rollup experience. Accordingly can go further and split up existing abstraction and implementation for tests to live in a separate sov-ibc-mocks crate.