Refactor Localhost

[colin-axner]

Summary

When creating connections and channels we do not store them under client prefixed stores. They are stored under the IBC prefix and then either channelEnds or connections. When verifying connection and channel states for light clients we pass the client prefixed store, so the client can access the consensus states if necessary. The localhost was using this client prefixed store to verify connections/channels. Unfortunately, connections and channels are not stored there, so this check would always fail.

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[cwgoes]

In principle, the localhost client should just have a read-only wrapper over the IBC store. Sounds like that might take awhile.

For now, I think it is reasonable to disable the localhost client.

[colin-axner]

Also relevant to fixing localhost Localhost acknowledgement verification needs to use types.CommitAcknowledgement

[colin-axner]

From cosmos/cosmos-sdk#7706

Localhost is just the chain ID and height of the current executing chain's context. We should support a dynamic query using the context. There is no need to store it and have custom logic in Create and Update client handling. We should refactor this out.

After further inquiry, we realized we cannot remove localhost from storage without injecting localhost logic into connection handshakes since the client won't always have access to the context. Instead we will remove localhost logic from ClientKeeper.CreateClient and ClientKeeper.UpdateClient and continue to store the localhost, since storage costs are tiny

We should just redesign the localhost's interaction with core IBC. cc @AdityaSripal for ideas on how to do this

[colin-axner]

ref #75

[colin-axner]

Localhost will be removed in v6 as there are no plans to fix it