Confusing s3 partSize configuration.

[zdyj3170101136]

issue

When uploading files through s3 bucket, I want to upload large files of 128MB through one http request to reduce s3 api fees.
So I set part_size to 128MB.

But after checking the source code of s3 upload, I found that when the uploaded file size is less than s3 partsize, partsize will be set to 0, and finally minio client will use 16MB part size when uploading, which is not what I expected.

objstore version

v0.0.0-20230220090313-0796692f1ae5