Add support for EKS Pod Identity

[tongshen-stephanie]

Issue #, if available: Closes #300

Description of changes:
Introduce an optional parameter usePodIdentity to support EKS Pod Identity

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 68.42105% with 72 lines in your changes missing coverage. Please review.

Project coverage is 52.62%. Comparing base (be94dd0) to head (4dd8774).
Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
...ntial_provider/pod_identity_credential_provider.go	70.43%	28 Missing and 6 partials ⚠️
auth/auth.go	31.42%	23 Missing and 1 partial ⚠️
credential_provider/irsa_credential_provider.go	83.33%	10 Missing ⚠️
provider/parameter_store_provider.go	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #416      +/-   ##
==========================================
+ Coverage   49.67%   52.62%   +2.94%     
==========================================
  Files           9       11       +2     
  Lines         781      952     +171     
==========================================
+ Hits          388      501     +113     
- Misses        383      436      +53     
- Partials       10       15       +5     

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[joebaro]

In this case there likely will not be an OIDC provider.

[tongshen-stephanie]

updated in commit 4d4df72