Add HostError context within each module-level error type

[seanchen1991]

Feature Summary

As we've defined and added the new HostError type into ibc-rs, a discrepancy has come about with how we've organized our errors at the top level. Specifically, the top-level error type contains module-level errors and then the HostError, which is not related to any one specific module. Instead, host errors, or errors that arise from any of the module-level handlers, can originate from any of the modules. Thus, it would be more appropriate to have a Host(HostError) variant within each of the module errors instead of in the top-level error type. This will incur duplication across our different error types, but in this case, the tradeoff of adding additional context that indicates a host-level error within a particular module justifies this duplication.

Proposal

Remove the Host(HostError) variant from the top-level HandlerError and add this variant to each of the module-level error types.