#3907387 Experiment: Restructure /me/security

Changes proposed in this Pull Request

• Push the new checklist format from #43101 to be the main nav for /me/security, which includes a split for actionable items versus informational ones. (Th
• To handle the above, push the change password page to /me/security/password.
• Restructure the individual pages under /me/security to use the HeaderCake component to provide a heading with a “Back” button to get back to the checklist at /me/security. (This isn’t implemented for the account settings, where we change email.)

Open Questions

• How should we handle the password link/text until we can actually implement the infrastructure to work out when the password was last changed.

Testing instructions

• Navigate to the live build at https://calypso.live/?branch=try/me-security-restructure
• After you get redirected to the current UI, check that /me/security works as before
• Manually add ?flags=security/security-checkup to the URL, and navigate to /me/security/.
• For each of the links, verify the following:
  • The link works
  • The page you navigate to includes a header with a “Back” button
  • The “Security” nav item on the left nav bar is selected for the page
  • Clicking on the “Back” button brings you back to the checklist at /me/security (except for the email row, as that navigates to /me/account)

Fixes #43144