feat: add ratelimiter package

What does this MR do?

First part of #627 (closed).

Adds a ratelimiter package using an lru.Cache that holds a "golang.org/x/time/rate".Limiter per source IP.

The rest of the functionality will be added in subsequent MRs.

TODO

• I added the Changelog trailer (e.g. Changelog: feature) to the commits that need to be included in the changelog
• I added unit tests or they are not required
• I added acceptance tests or they are not required
• I added documentation (or it's not required)
• I followed code review guidelines
• I followed Go Style guidelines