Remove ServiceMetadata usage from DefaultS3Presigner, S3Utilities,and DefaultPollyPresigner

[S-Saranya1]

Motivation and Context

Remove ServiceMetadata dependency from DefaultS3Presigner, S3Utilities, and DefaultPollyPresigner. These three classes call AwsClientEndpointProvider with serviceEndpointPrefix/defaultProtocol/region, which triggers the expensive clientEndpointFromServiceMetadata() code path — loading GeneratedServiceMetadataProvider and incurring 350-500ms static initialization overhead. This is part of the ServiceMetadata removal work, feature branch - feature/master/remove-service-metadata-usage

Modifications

• DefaultS3Presigner: Use resolveFromOverrides() to check for endpoint overrides/environment. If none found, use https://localhost placeholder (marked as not overridden) — S3ResolveEndpointInterceptor replaces it with the real endpoint during presigning. Added region validation at build time for fail-fast on invalid regions.

• S3Utilities: Same approach — resolveFromOverrides() with localhost fallback. The endpoint is replaced by S3EndpointProvider during the getUrl() flow.

• DefaultPollyPresigner: Use resolveFromOverrides() to check for overrides/environment. If none found, call PollyEndpointProvider (Endpoints 2.0) directly to get an accurate endpoint. Unlike S3, the Polly presigner has no downstream endpoint resolution — the endpoint becomes the final presigned URL host.

• InvalidRegionTest: Updated assertions to match new error messages. S3Utilities errors now come from S3EndpointProvider ("Invalid region: region was not a valid DNS name.") and S3Presigner errors come from build-time validation ("Configured region .. resulted in an invalid URI"). the exception type is same, but the error message slightly varies( the exception type and fail-fast behavior are preserved).

Testing

• Existing S3PresignerTest and S3UtilitiesTest suites validate full endpoint URLs (virtual-hosted, path-style, accelerate, dualstack, overrides) — any localhost leak would immediately fail these tests.
• Updated InvalidRegionTest assertions to match new error messages.
• Added presign_noEndpointOverride_usesDefaultEndpoint test in DefaultPollyPresignerTest to verify that the Endpoints 2.0 fallback produces the correct host (polly.us-east-1.amazonaws.com).

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• I have read the CONTRIBUTING document
• Local run of mvn install succeeds
• My code follows the code style of this project
• My change requires a change to the Javadoc documentation
• I have updated the Javadoc documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed
• I have added a changelog entry. Adding a new entry must be accomplished by running the scripts/new-change script and following the instructions. Commit the new file created by the script in .changes/next-release with your changes.
• My change is to implement 1.11 parity feature and I have updated LaunchChangelog

License

• I confirm that this pull request can be released under the Apache 2 license

[zoewangg]

Any reason we are not using localhost like we do in other presigners?

[S-Saranya1]

Unlike other presigner the Polly presigner has no downstream endpoint resolution. The endpoint resolved here is the final presigned URL, so it must be a real endpoint, not a placeholder.

[github-actions]

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