feat: expose internal providers && support init client with provider

[yndu13]

You need to complete

• unit tests and/or feature tests
• documentation is changed or added

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 62.79070% with 32 lines in your changes missing coverage. Please review.

Project coverage is 97.51%. Comparing base (47c2eab) to head (2d0e2b4).

Files with missing lines	Patch %	Lines
credentials/providers/ram_role_arn.go	38.46%	26 Missing and 6 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #125      +/-   ##
==========================================
- Coverage   98.74%   97.51%   -1.23%     
==========================================
  Files          30       30              
  Lines        2467     2534      +67     
==========================================
+ Hits         2436     2471      +35     
- Misses         21       47      +26     
- Partials       10       16       +6     

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