Show Duo Pro button for ultimate trial

What does this MR do and why?

Show start a Duo Pro button on the group billing page for ultimate trial plans

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Desktop	Mobile

How to set up and validate locally

bin/rails c

Feature.enable(:cs_connect_with_sales)
Feature.enable(:duo_pro_trials)

• Setup gdk to simulate SaaS - https://docs.gitlab.com/ee/development/ee_features.html#simulate-a-saas-instance and restart GDK
• Sign in. Create 1 group.

bin/rails c

GitlabSubscription.last.update(hosted_plan: Plan.find_by(name: 'ultimate_trial'), trial_starts_on: 1.days.ago, trial_ends_on: 29.days.from_now, trial: true)

• Visit group billing page.
• Verify Start a free GitLab Duo Pro trial button is present.

Related to #451013