Improve tests for MultipleFileUpload

从 MultipleFileUpload 组件及其现有的 snapshot 测试开始。检查第三方库的 onFileDrop 行为目前是如何表示的，然后为返回的 File 路径以及它与单文件上传之间的差异添加有针对性的覆盖。完成标准是相关行为得到了测试，而不仅仅是由 snapshots 覆盖。

Describe the enhancement or change
Consumer reported the following:

Not really an issue, but I am puzzled by the slight behaviour change of the MultipleFileUpload component.
The onFileDrop callback sends an array of File objects, with properties like path. But it seems this propetrty
changed a little bit:
In PF5 I was getting for example: path: "image.png"
In PF6 I am getting: path: "./image.png"
That's not much of a change and is almost the same in a filesystem. But as I was using this info for the path of the object I am sending into Object Storage, it messed up my app a little bit.
Again, not an issue, I will handle it in my code, but I was wondering if there was a specific reason for this behaviour change? Which does not happen for single file upload btw, it's the plain name of the file only.

We use a third-party library for this piece of the component - we did bump from 14.2.3 to 14.3.5 between versions, so it's possible they changed the file name handling between versions. I don't see a big difference in our code. I do see that we have mostly snapshot tests for this component and do not test the third-party library functionality at all in our tests, so we wouldn't have caught this when we bumped the dependency. We could stand to improve our tests for this component in my opinion.

Is this request originating from a Red Hat product team? If so, which ones and is there any sort of deadline for this enhancement?
No - not blocking.

Jira Issue: PF-1855