…ublisher of ClosableAsyncRequestBody and use it in s3 multipart client

Motivation and Context

• This PR introduces a new split method, splitClosable in AsyncRequestBody that returns an SdkPublisher of ClosableAsyncRequestBody instead of AsyncRequestBody, enabling proper resource management for split request bodies. The change is primarily implemented to support streaming retry for S3 multipart client for retry Support retries for individual parts of a multipart upload in Java SDK V2 #6198

• Introduces ClosableAsyncRequestBody interface extending AsyncRequestBody with close capability

• Updates S3 multipart client implementation to use the new splitClosable method

Testing

Added wiremock tests

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