feat: LEAP-818: Add X-Api-Key support

[jombooth]

If X-API-Key header is specified with <token>, overwrite the Authorization header with Token <token>.

Resolves #3349

~/Repos/label-studio on  fb-LEAP-818/x-api-key [$?]
❯ curl -X GET http://localhost:8080/api/projects/ -H 'X-API-Key: [redacted]'
{"count":27,"next":null,"previous":null,"results":[...]}

HttpRequest.META documentation for reference: https://docs.djangoproject.com/en/5.0/ref/request-response/#django.http.HttpRequest.META

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.79%. Comparing base (40e174b) to head (54214d4).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #5562      +/-   ##
===========================================
+ Coverage    75.77%   75.79%   +0.01%     
===========================================
  Files          157      157              
  Lines        13125    13133       +8     
===========================================
+ Hits          9946     9954       +8     
  Misses        3179     3179              

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