Fix to encode/decode credential id as base64url

[abcang]

Target branch: 4.9.x Resolves issue #

• [x] It is a Bug fix
• [ ] It is a New feature
• [ ] Breaks BC
• [ ] Includes Deprecations

Previously, the id of the PublicKeyCredential obtained by the PublicKeyCredentialDenormalizer was a raw base64url encoded string sent by the browser. However, with change #589, it is now converted to a base64-encoded string. This pull request reverts this behavior back to the previous one.

Also, I think it is correct to decode if only $id is passed when creating an instance, so I fixed this as well.

[Spomky]

Many thanks!

[abcang]

Thank you for fixing my mistake and merging my pull request!