Increase default chunk size for async request

[Fred1155]

Motivation and Context

According to public S3 documentation, https://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-streaming.html , the chunk size is recomended to be at least 64 Kb to achieve better performance. The current default chunk size for sync is 128 KB and default chunk size for async is 16 Kb.

Modifications

Increase the DEFAULT_ASYNC_CHUNK_SIZE from 16Kb to 64Kb

Testing

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

[dagnir]

The current default chunk size for sync is 128 KB

should we just increase to 128 KB to be consistent with sync?

[zoewangg]

This is only used by legacy code, right?