Streamline Msg trait definition

[Farhad-Shabani]

Context

The Msg trait definition within the ibc-primitives can be streamlined because:

• With the release of ibc-proto-rs v0.38.0, the Protobuf trait is now re-exported from tendermint-proto. This Protobuf is not object-safe, and it is no longer necessary to satisfy earlier conditions that was limiting us to use Protobuf as a trait bound for other traits, thereby we now can discard the get_sign_bytes method.

• Another update comes from prost v0.12.3, introduced as of ibc-proto-rs v0.39.1. With this version, we gain access to the auto prost::Name derive, which implements a similar method to the type_url method. Therefore, with the proper type restriction, the type_url method becomes obsolete too.

• Additionally, the Msg trait's naming should be more reflective of its broader use case. It can now be implemented on other types beyond IBC messages, such as ClientState. In general, this trait defines the interaction/conversion between a domain type and its associated proto types.

Prerequisites

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1. Update ibc-proto-rs to v0.39.1 #994
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