Add Rate Limiter integration to Messenger

I created a stacked MR on top of Retry/Failed ( ✨ Implement retry Active ) MR, which is stacked on DrupalSQL ( 📌 Provide a Drupal SQL transport Active ) MR.

https://git.drupalcode.org/project/sm/-/merge_requests/34

dpi → credited lussoluca → .

I've removed the sm_test_rate_limiter submodule, and I've added a section in the readme about how to configure the rate limiter

Merged, thanks @lussoluca

Automatically closed - issue fixed for 2 weeks with no activity.