POC: POC branch for external file implementation using cloud auth

[Akshay2191]

Did a POC to see the imports required to add the file fetching and auth features directly in Agent code for 3 cloud providers
AWS,Azure,GCP

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING document
• I have run make install-tools and have attached any dependency changes to this pull request
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• If applicable, I have updated any relevant documentation (README.md)
• If applicable, I have tested my cross-platform changes on Ubuntu 22, Redhat 8, SUSE 15 and FreeBSD 13

[codecov]

Codecov Report

❌ Patch coverage is 64.12698% with 113 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.88%. Comparing base (b1947ec) to head (1fa0c17).
⚠️ Report is 78 commits behind head on external-file-mgmt-integration.

Files with missing lines	Patch %	Lines
internal/file/file_manager_service.go	56.86%	102 Missing and 8 partials ⚠️
internal/config/config.go	95.23%	1 Missing and 1 partial ⚠️
internal/file/file_service_operator.go	94.44%	1 Missing ⚠️

Additional details and impacted files

@@                        Coverage Diff                         @@
##           external-file-mgmt-integration    #1462      +/-   ##
==================================================================
- Coverage                           86.31%   85.88%   -0.43%     
==================================================================
  Files                                 102      102              
  Lines                               12603    12882     +279     
==================================================================
+ Hits                                10878    11064     +186     
- Misses                               1249     1333      +84     
- Partials                              476      485       +9     

Files with missing lines	Coverage Δ
internal/config/defaults.go	100.00% <ø> (ø)
internal/config/flags.go	100.00% <ø> (ø)
internal/config/types.go	87.65% <ø> (ø)
internal/model/config.go	90.47% <ø> (ø)
internal/file/file_service_operator.go	76.82% <94.44%> (+0.68%)	⬆️
internal/config/config.go	87.60% <95.23%> (+0.29%)	⬆️
internal/file/file_manager_service.go	66.93% <56.86%> (-8.46%)	⬇️

... and 6 files with indirect coverage changes

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[Akshay2191]

This feature will be done by NGINXSaas team This PR was open as a part of POC to see how much the agent binary will increase if we add all the dependant packages directly to agen.