support AWS S3 region parsing for 4-part regions

[Igor-splunk]

Description

Fixes AWS S3 region parsing to support 4-part regions like us-gov-west-1, us-iso-east-1, and us-isob-east-1. The previous regex only matched 3-part regions (e.g., us-west-2), causing App Framework to fail when using GovCloud or ISO endpoints.

Key Changes

• pkg/splunk/client/awss3client.go: Updated regionRegex from ([a-z]+-[a-z]+-[0-9]+) to ([a-z]+-[a-z]+(?:-[a-z]+)?-[0-9]+) to make the third region component optional
• pkg/splunk/client/awss3client_test.go: Added TestGetRegion() with 10 test cases covering standard (3-part), GovCloud (4-part), and ISO regions, plus error scenarios

Testing and Verification

• Added comprehensive unit tests validating region extraction for:
  • Standard regions: us-west-2, eu-west-1
  • GovCloud regions: us-gov-west-1, us-gov-east-1
  • ISO regions: us-iso-east-1, us-isob-east-1
  • Bucket prefix variations and invalid endpoints

Related Issues

#1567

PR Checklist

• Code changes adhere to the project's coding standards.
• Relevant unit and integration tests are included.
• Documentation has been updated accordingly.
• All tests pass locally.
• The PR description follows the project's guidelines.

[coveralls]

Pull Request Test Coverage Report for Build 18688544828

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.008%) to 86.544%

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Files with Coverage Reduction	New Missed Lines	%
pkg/splunk/enterprise/afwscheduler.go	1	92.9%

Totals
Change from base Build 18653942794:	-0.008%
Covered Lines:	10709
Relevant Lines:	12374

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💛 - Coveralls