[Enhancement] The path prefix can be flexibly specified when create a HDFS Storage Vault.

### Search before asking

- [x] I had searched in the [issues](https://github.com/apache/doris/issues?q=is%3Aissue) and found no similar issues.

### Description

In3.x/4.x versions, some customers often enter an incorrect value for path_prefix when creating an HDFS storage vault. Sometimes, they may add a prefix /xxx, which will result in an error. We can optimize the prefix writing by allowing the prefix /xxx to be added, thus making the writing more flexible.

### Solution

_No response_

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

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