Implement OAuth 2.0 Token Exchange credentials provider in Go SDK

[UgnineSirdis]

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Implement OAuth 2.0 Token Exchange credentials provider in Go SDK

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Issue Number: 3542

What is the new behavior?

Other information

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 85.34323% with 79 lines in your changes are missing coverage. Please review.

Project coverage is 40.81%. Comparing base (f27b85b) to head (62940fe).
Report is 78 commits behind head on master.

Files	Patch %	Lines
credentials/options.go	0.00%	44 Missing ⚠️
internal/credentials/oauth2.go	95.00%	17 Missing and 7 partials ⚠️
credentials/credentials.go	0.00%	6 Missing ⚠️
options.go	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1194      +/-   ##
==========================================
+ Coverage   40.06%   40.81%   +0.75%     
==========================================
  Files         308      309       +1     
  Lines       32208    32747     +539     
==========================================
+ Hits        12903    13367     +464     
- Misses      18885    18955      +70     
- Partials      420      425       +5     

Flag	Coverage Δ
go-1.21.x	42.93% <94.06%> (+0.91%)	⬆️
go-1.22.x	40.80% <85.34%> (+0.75%)	⬆️
macOS	40.35% <84.18%> (+0.74%)	⬆️
ubuntu	40.34% <84.18%> (+0.71%)	⬆️
unit	40.81% <85.34%> (+0.75%)	⬆️
windows	40.81% <85.34%> (+0.75%)	⬆️

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