Follow-ups for passkey support in ASP.NET Core Identity

[MackinnonBuck]

#62112 adds support for passkeys in ASP.NET Core Identity and extends the Blazor Web App template to support passkey management and authentication. However, there are some follow-up items we should consider:

• Update Microsoft.AspNetCore.Identity.UI to support the same passkey UI that got added to the Blazor Web App template
• Update scaffolding to include passkey support
• Extend the Blazor Web App template, Identity UI, and scaffolding to support passwordless account creation
• Enable WebAuthn conformance testing in CI
  • There's currently a project in this repo that can be run against the FIDO2 Conformance Test tool, but the tool itself is proprietary and doesn't have a CLI. We should consider writing our own solution that performs similar validations to the conformance testing tool.
• Support conditional create to allow the user to seamlessly upgrade a password to a passkey after signing in
• Use the signals API to, e.g., inform the authenticator when a passkey was revoked so it doesn't get presented to the user as an option when signing in
• Make it easy to configure well-known passkey endpoints so that authenticators can automatically upgrade passwords to passkeys without requiring the customer to visit the site