Duo Pro Self-managed Trial

Step 1: What is changing in this MR?

This MR creates a new Self Managed GitLab Duo sales form.

• Contentful Entry - Needs to be edited
• 4146 - Id of Marketo Form that we're testing

Production	Review app
N/A	https://3445-self-managed-duo-sales.about.gitlab-review.app/solutions/gitlab-duo-pro/self-managed-and-gitlab-dedicated-trial/

Closes https://gitlab.com/gitlab-com/marketing/digital-experience/buyer-experience/-/issues/3445

Step 2: Ensure that your changes comply with the following, where applicable:

• I, the Assignee, have run Axe tools on any updated pages, and fixed the relevant accessibility issues.
• These changes work on both Safari, Chrome, and Firefox.
• These changes have been reviewed for Visual Quality Assurance and Functional Quality Assurance on Mobile, Desktop, and Tablet.
• These changes work with our Google Analytics and SEO tools.
• These changes have been documented as expected.

Build Variables:

• Use Contentful Preview API

Closes #3445