feat: use authenticate endpoint for x

[aeneasr]

Improves the "Log in with X" experience by not asking the user to re-authenticate every time.

Related issue(s)

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
  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 or changed the documentation.

Further Comments

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes are missing coverage. Please review.

Project coverage is 77.97%. Comparing base (9ddf7cc) to head (e76546b).
Report is 1 commits behind head on master.

Files	Patch %	Lines
selfservice/strategy/oidc/provider_x.go	0.00%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3833      +/-   ##
==========================================
+ Coverage   77.95%   77.97%   +0.01%     
==========================================
  Files         358      358              
  Lines       25165    25169       +4     
==========================================
+ Hits        19617    19625       +8     
+ Misses       4041     4037       -4     
  Partials     1507     1507              

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