Migrate badge styles for system notes stored in DB

Migrate styles in https://gitlab.com/gitlab-org/gitlab/-/blob/cc236b185835756f4e997ebcd2ec3c9363f50943/app/assets/stylesheets/bootstrap_migration_components.scss#L80-100 to use badge design tokens. Potentially move from bootstrap_migration_components.scss into a file which describes the behaviour more clearly.