Resolve "Prepare project for launch: content and domain updates"

What does this MR do and why?

This MR gets Hugo project ready for launch:

• Find/replace all references of new.docs.gitlab.com in docs-gitlab-com
• Copy over any updates to google-site-verification tags from gitlab-docs
• Copy over any updates to landing.yaml from gitlab-docs
• Update navigation.yaml

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Configure a local GitLab Docs environment: https://gitlab.com/gitlab-org/technical-writing/docs-gitlab-com/-/blob/main/doc/setup.md.

Merge request acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this merge request.

Closes #183 (closed)