[EPIC] Rate limiting middleware

[gjermundgaraba]

The goal of this epic is to move the rate-limiting middleware module that currently resides at https://github.com/cosmos/ibc-apps/tree/main/modules/rate-limiting into the ibc-go repo to be maintained by the core IBC team.

Brief overview over things that need to be done

• Set up the rate-limiting module as a separate go module under modules/apps and move and rename proto files to use the same structure and package names we use in the ibc-go repo for other middlewares
• Move all the logic over to this repo
• Upgrade to use ibc-go/v10
• Refactor to follow the same structures and conventions used in the ibc-go repo
• Write any missing unit and integration tests to at least cover the same type of scenarios as we do in callbacks and ics-29
• Write e2e tests under e2e/
• Add support for Eureka packets by adding a v2 middleware (see callbacks to see how to do this)
• Write unit and integration tests
• Write e2e tests (we still need to figure out how we do e2e testing for Eureka in this repo as we are lacking good relaying capabilities)

👋 Note: we need to take notes on any missing information in the upgrade docs for middleware going from v8 to v10