iam: implement identity APIs for AWS substrate

[SriramGuduri]

Summary

< Provide a brief description of the changes in this PR >

Some conventions to follow

1. add the module name as a prefix
   • for example: add a prefix: docstore: for document store module, blobstore for Blob Store module
2. for a test only PR, add test:
3. for a perf improvement only PR, add perf:
4. for a refactoring only PR, add "refactor:"

[codecov-commenter]

Codecov Report

❌ Patch coverage is 46.82540% with 67 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.64%. Comparing base (9066147) to head (a80dbd5).

Files with missing lines	Patch %	Lines
...ava/com/salesforce/multicloudj/iam/aws/AwsIam.java	53.63%	37 Missing and 14 partials ⚠️
...lesforce/multicloudj/iam/aws/ErrorCodeMapping.java	0.00%	16 Missing ⚠️

❌ Your patch status has failed because the patch coverage (46.82%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #225      +/-   ##
============================================
- Coverage     83.19%   82.64%   -0.56%     
- Complexity       94      110      +16     
============================================
  Files           150      152       +2     
  Lines          8195     8321     +126     
  Branches        952      979      +27     
============================================
+ Hits           6818     6877      +59     
- Misses          926      979      +53     
- Partials        451      465      +14     

Flag	Coverage Δ
unittests	82.64% <46.82%> (-0.56%)	⬇️

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