[6.x] Fix creating passkeys

[duncanmcclean]

This pull request fixes an issue preventing passkeys from being created.

Problem

The web-auth/webauthn-lib package recently changed what is returned by the assertionResponseValidator->check() method.

It previously returned a PublicKeyCredentialSource instance but it now returns a CredentialRecord instance, causing a type error in our code.

Solution

This PR fixes it by accepting any object (as CredentialRecord only exists in 5.3.x) and converting the CredentialRecord to what we're expecting.

These changes are part of the package's 5.3.x branch which is yet to be tagged, but seems to be used when creating new Statamic sites.

An alternative solution would be to pin the package to 5.2.x and handle the necessary changes after 5.3.x has been tagged.

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Fixes #13561