Replaced ruby regexp with UntrustedRegexp which uses RE2

This MR replaces the usage of Ruby's built-in regexp with RE2, which helps prevent potential abuse. For now, this MR introduces just enough of GitLab's UntrustedRegexp to replace the current usage of gsub. However, in the future it would be best to allow UntrustedRegexp to be its own gem so that this gem, GitLab's monorepo, and any other gems we may need to build outside the monorepo can share this module.

This is related to https://gitlab.com/gitlab-org/gitlab/-/issues/455013 which has been approved to be a security-fix-in-public https://gitlab.com/gitlab-org/gitlab/-/issues/455013#note_1944450170