SSO MFA tracker

[Joerger]

Tracker issue for SSO MFA.

• RFD 180: SSO as MFA Method #44699
• Add second_Factors #47233
  • Related: deprecate second_factor without removing it
    • Deprecate second factor off/optional (mostly consists of updating tests / adding backdoor via testing modules)
    • Update MFA Web login endpoint to support OTP, remove reliance on knowing second_factor in the client. Makes ^ simpler.
• feat: SSO MFA - Add Auth Connector MFA settings protobuf and methods. #46687
• feat: SSO MFA - support for SAML ForceAuthn for login and mfa checks #46703
• feat: SSO MFA - Add ephermeral SSO MFA device #46704
• SSO MFA Challenge and Response
• SSO MFA IdP flow
• feat: SSO MFA - Add SSO MFA ceremony #46982 (tctl and tsh)
  • prereq: Unify and simplify MFA Ceremony helpers #46986
  • prereq: SSO Ceremony refactor #46983
  • Add WebUI ceremony
  • Add Teleport Connect ceremony
• Documentation