refactor(raw): Return written bytes in oio::Write

[Xuanwo]

This PR will add written bytes into oio::Write.

Background

The oio::Write function was originally designed to ensure that both the write and sink operations write all content at once, in order to make it easier to use. However, this behavior creates a significant amount of additional work for services that need to ensure reentrancy in their writes.

In some cases, such as with HDFS, implementing this behavior becomes impossible due to limitations like lack of support for seek write.

Additionally, it places a heavy burden on correctly implementing buffer logic because all operations must be reentrant. As a result, more content needs to be buffered and returned when required.

Current

This PR just adds a written bytes into oio::Write, public API like Writer::write is not touched. Writer::sink and Writer::copy changed to return written bytes which should be treated as a breaking change.

No services side behavior change yet. In the future, we will change the fs and hdfs's implement so that we don't need to call write_all and maintain internal pos.

[suyanhanx]

Thanks.

[suyanhanx]

Do you have any subsequent changes planned? Or open an issue if you can?

[Xuanwo]

Do you have any subsequent changes planned? Or open an issue if you can?

I'm still exploring.