fix: improve OIDC account linking UI

[jonas-jonas]

Improves the account linking UI, to only show relevant options to the user. E.g. if the user previously registered using a password, but tries to log into the account using Google, we only show the password input. Similarly, if they used Apple the first time, and Google on the next login, they would only see the Apple login button. If they have both a password and Apple set up, Ory Kratos will show both as options.

Related issue(s)

Fixes #5983

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• 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 the approval (please contact
  [email protected]) 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 or changed the documentation.

Further Comments

[codecov]

Codecov Report

Attention: Patch coverage is 95.58824% with 3 lines in your changes missing coverage. Please review.

Project coverage is 78.41%. Comparing base (76af303) to head (34cd276).
Report is 3 commits behind head on master.

Files	Patch %	Lines
selfservice/strategy/oidc/strategy.go	93.47%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4036      +/-   ##
==========================================
+ Coverage   78.39%   78.41%   +0.02%     
==========================================
  Files         370      370              
  Lines       26127    26155      +28     
==========================================
+ Hits        20481    20509      +28     
  Misses       4088     4088              
  Partials     1558     1558              

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[hperl]

This looks very nice! I just added two comments below, but nothing major. Brilliant!

[hperl]

LGTM!

[aeneasr]

Needs a merge, then good to go!