Configure error tracking to use latest Sentry

What does this MR do and why?

Related to https://gitlab.com/gitlab-org/gitlab/-/issues/393741#note_1302062282

We have configured a shiny new Sentry server and we're also sending the production Rails errors to it: https://new-sentry.gitlab.net/organizations/gitlab/projects/rails/?environment=gprd&project=3

This MR tries to update the error tracking code for this project to also use the new server. I didn't completely replaced sentry-raven with sentry-ruby because I don't want the process to be disruptive, we can run both of them at the same time and when everything with the new server is stable, we can remove the old SDK.

Deployments::SentryTracker will be handled in a new MR.

Author Check-list

• Has documentation been updated?