Support `Operator::remove_all` in huaweicloud OBS Parallel File System

### Describe the bug

Huaweicloud OBS has concept of directory, which isn't part of S3 protocol.

This difference brings some issues when performing recursive deletion.

For example, if we are trying to invoke `Operator::remove_all` on a prefix, it will try to `stat` the prefix first. OBS will return a directory object which cannot be deleted(will cause `DirectoryNotEmpty` error) if there is still objects in the directory.

### Steps to Reproduce

```rs
op.write_with("/path/to/obj", payload).await.unwrap();

op.remove_all("/").await.unwrap(); // this will return error
```

### Expected Behavior

No error.

### Additional Context

_No response_

### Are you willing to submit a PR to fix this bug?

- [ ] Yes, I would like to submit a PR.

Start at the Operator::remove_all entry point and reproduce the issue with the provided Rust snippet against Huaweicloud OBS Parallel File System. Trace how the OBS directory object is handled during recursive deletion; done means removing the prefix containing /path/to/obj completes without a DirectoryNotEmpty error.

Written by the indexing model from the issue text.