Currently drag and drop expects to selection to be in the same folder,
but blender internal file browser allows to select files from different
folders when recursion is active.
When writing to operator properties the `directory` is taken now from
the first file provided, and `files` are now relative to this
`directory` instead of just taking the file name.
When reading from operator properties filepaths are normalized.
I notice this issue while reading about #140942, the issue would
require a proper fix too.
Pull Request: https://projects.blender.org/blender/blender/pulls/140948
d441ac2d6f