### What changes were proposed in this pull request?
- close [CELEBORN-1911](https://issues.apache.org/jira/browse/CELEBORN-1911)
This PR refactors the project structure by moving the multipart-uploader module into multipart-uploader/multipart-uploader-s3.
### Why are the changes needed?
This change improves modularity and enables future extensions, such as multipart-uploader/multipart-uploader-oss, allowing better support for multiple object storage backends.
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
Deployment integration testing has been completed in the local environment.
Closes#3153 from shouwangyw/optimize/mpu-s3.
Authored-by: veli.yang <897900564@qq.com>
Signed-off-by: mingji <fengmingxiao.fmx@alibaba-inc.com>
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