feat(sdk): allow setting of extra headers for the gql client

[dmitryduev]

Description

Provide a temporary way to pass extra headers to the GraphQL Client init.

TODO: Shall be refactored once the Settings refactor is complete.

Testing

How was this PR tested?

Checklist

• Include reference to internal ticket "Fixes WB-NNNN" and/or GitHub issue "Fixes #NNNN" (if applicable)
• Ensure PR title compliance with the conventional commits standards

[vanpelt]

Thanks for doing this @dmitryduev !

[codecov]

Codecov Report

Merging #5237 (5e0f740) into main (1cdafd4) will increase coverage by 0.00%.
The diff coverage is 100.00%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5237   +/-   ##
=======================================
  Coverage   82.73%   82.73%           
=======================================
  Files         311      311           
  Lines       38397    38400    +3     
=======================================
+ Hits        31767    31770    +3     
  Misses       6630     6630           

Flag	Coverage Δ
functest	55.75% <100.00%> (+0.02%)	⬆️
unittest	73.07% <100.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
wandb/sdk/lib/_settings_toposort_generated.py	100.00% <ø> (ø)
wandb/sdk/internal/internal_api.py	89.59% <100.00%> (-0.11%)	⬇️
wandb/sdk/internal/settings_static.py	94.93% <100.00%> (+0.06%)	⬆️
wandb/sdk/wandb_settings.py	94.33% <100.00%> (+<0.01%)	⬆️

... and 3 files with indirect coverage changes

[raubitsj]

Good enough for now.