feat(GlToast): Replace BootstrapCSS Util with GitLab UI Class

mentioned in commit 06012b08

mentioned in merge request gitlab-org/frontend/playground/accessibility-scanner!55 (closed)

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!352 (merged)

mentioned in merge request status-page!903

mentioned in merge request gitlab!171760 (closed)

mentioned in commit 79de5412

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!4168 (merged)

mentioned in merge request gitlab!172328 (closed)

mentioned in merge request gitlab-org/editor-extensions/gitlab-jetbrains-plugin!1249 (closed)

mentioned in commit 94c182b6

mentioned in merge request gitlab-org/frontend/playground/accessibility-scanner!58 (merged)