Geo Logger should use the same log level defined in Rails

What does this MR do?

Use the same log level defined in Rails.logger.level for the Gitlab::Geo::Logger

Are there points in the code the reviewer needs to double check?

I voided modifying this in a root Logger class, because I don't understand every Logger use-case. As common sense I would say we could do that for whole GitLab setup, but this should probably be discussed in a different issue.

Why was this MR needed?

The amount of "detail" we are generating in Geo is too much for some customers: https://gitlab.com/gitlab-org/gitlab-ee/issues/4497#note_53737909

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Review
  • Has been reviewed by Backend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #4497 (closed)