fix: oidc should show pre-filled traits and missing traits

[Benehiko]

When in an OIDC flow the traits of the prefilled data might be missing once redirected back from the OIDC provider.

1. Login with X
2. Redirect back to registration page
3. Show prefilled traits it could populate & missing traits (error)
4. Enter missing traits and click continue

Step 3 works since the traits are still mapped under a different group:

In some cases the UI would be shown with only a continue button if an error occurred on a non-oidc group. This would thus create an empty form with only the continue button.

Related Issue or Design Document

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• [ ] I have referenced an issue containing the design document if my change introduces a new feature.
• [ ] I have read the security policy.
• [ ] I confirm that this pull request does not address a security vulnerability. If this pull request addresses a security vulnerability, I confirm that I got approval (please contact security@ory.sh) from the maintainers to push the changes.
• [ ] I have added tests that prove my fix is effective or that my feature works.
• [ ] I have added the necessary documentation within the code base (if appropriate).

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