USWDS v3 upgrade: Ensure MHV landing page is not broken

[wesrowe]

Description

User story

As a Cartographers team member, I want to opt all landing page components into v3 "manually" ahead of the full deprecation and automatic cut-over, so that we can make sure that our page will continue to look and function right.

Notes

• Upgrade is being done by DST in stages, from opt-in to opt-out to forced.
• list of components impacted by this work is in the side-bar of Storybook
• QA approaches and tech debt:
  • AuthExpt thread clarifies that tech debt will be left over (a uswds attribute in html)
  • If we merge opt-in code for the sake of QA-ing the landing page with v3, we will want to later remove it again
• Dates have been shifting (currently 4/19 5/3 deprecation, with auto-opt-in 5/6) – need to monitor team of teams and slack for updated final deprecation date – @LynneJohnson224 @wesrowe
• Threads from DST in vfs-change-announcements:
  • original announcement
  • further reminder

Possible tasks:

• [x] OPT OUT immediately, get PR into prod by Friday EOD
• [x] See if we have a v3 problem
• [x] Fix v3 problem

Acceptance criteria

• Tested (in agreed-upon environment) whether v3 upgrade will break any aspects of landing page looks or functionality
• Got UX review of page with v3 components
• Got a11y review of page with v3 components
• Fixed any issues in production codebase
• Ticketed future removal of any code that will become tech debt after full deprecation of v1 (e.g., any uswds flags)

[jzucadi]

PR for opting out of uswds: https://github.com/department-of-veterans-affairs/vets-website/pull/28285

[jzucadi]

PR for opting out has been merged Mar 1, 2024

[jzucadi]

PR for using USWDS ver 3 components