Change `AuthenticatorSelection.Default`to prefer ResidentKey (discoverable keys)

[abergs]

With the move towards passkeys I think having the default AuthenticatorSelection discourage discoverable keys is wrong.
Let's embrace this momentum and change the default to prefer a resident key.

Discussion Points

I'd appreciate community feedback on this change, particularly regarding:

• Security implications
• User experience trade-offs
• Specific use cases where this might be problematic