Enhance Security & Compliance Error Handlings

This commit solves: https://gitlab.com/gitlab-org/gitlab/-/issues/386854
It enhances the error handling for the Security & Compliance Configuration
to make the distinction between user-facing and non-user facing errors.
To achieve this behaviour this commit introduces a Backend and a
Frontend util to make User facing errors distinguishable by adding
and parsing a prefix.

Changelog: changed
EE: true