Move serializers.rs module into ibc-primitives

[Farhad-Shabani]

Summary

The custom (de)serializer module, initially utilized by the ICS-20 application, is now used by the ICS-721 too, and would serve other IBC applications, such as ICS-27.

Proposal

It is advisable to centralize this module under the ibc-primitives to avoid redundancy and streamline maintenance. This ensures broader reusability, enabling developers of any IBC application built upon the ibc-rs libraries to benefit from.