[meta] Update product badges

Per the new policy https://about.gitlab.com/handbook/marketing/product-marketing/#tiers

• STEP 1: Update badges: release post, features, comparison: "CE, EES, EEP, EEU" => "Libre, Starter, Premium, Ultimate" => #1902 (closed) => !9645 (merged)
• STEP 2: Add new badges for GitLab.com "Free, Bronze, Silver, Gold" => #1904 (closed) => !9668 (merged)
  • STEP 3: Replace variables gitlab_ce, gitlab_ees, gitlab_eep, gitlab_ees, with gitlab_libre, gitlab_starter, gitlab_premium, gitlab_ultimate => #1908 (closed) => !9677 (merged)
• STEP 4: Redesign: ask UX to find a way to not display 8 badges at the same time => #1907 (closed)
• STEP 5: Update the documentation => https://gitlab.com/gitlab-org/gitlab-ce/issues/42631 // https://gitlab.com/gitlab-com/gitlab-docs/issues/173 > https://gitlab.com/gitlab-com/gitlab-docs/merge_requests/244 // https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/18408 // https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/5381
• STEP 6: Update the handbooks and templates

Related tasks:

• Update release post description (https://about.gitlab.com/2018/01/22/gitlab-10-4-released/#gitlab-products) => !9735 (merged)
• Update patch release post templates (10.5+) => !10269 (merged)