Create rate-limiting middleware module

[gjermundgaraba]

We still need to discuss how we split up the epic, so this task can include some or all of the below:

• 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
• Refactor to follow the same structures and conventions used in the ibc-go repo
• Have at least a one "happy path" integration tests (that limits the rate correctly)
• Integrate into the simapp
• Have at least one "happy path" e2e test (that limits the rate correctly)

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