Generalize credential public key return value

[grzuy]

Right now in response#credential we're returning the public key in EC point uncompressed format.

We need to change that to become agnostic of the public key type.

[grzuy]

We probably just want to return the exact bytes in the credentialPublicKey field in https://www.w3.org/TR/webauthn/#credentialpublickey.

[grzuy]

This change needs to be backwards-compatible by keeping support for the EC point uncompressed format in the allowed_credentials option for the AuthenticatorAssertionResponse#verify method.

So that current apps with stored credentials don't break.

[grzuy]

FWIW this will make us comply more precisely with step 18 in https://www.w3.org/TR/webauthn/#registering-a-new-credential.

[...] by associating it with the credentialId and credentialPublicKey in the attestedCredentialData in authData, as appropriate for the Relying Party's system.

[grzuy]

Released in v1.12.0