add fields: path and download_uri for ArtifactoryFileStat

[donhui]

add fields: path and download_uri for ArtifactoryFileStat.

[allburov]

Thanks @donhui! I went a slightly different route in #504 and credited you as co-author.

Instead of adding the fields to the ArtifactoryFileStat namedtuple, it adds ArtifactoryPath.stat_json(), which returns the File Info response as-is — so you get downloadUri and path, plus anything else the server sends:

stat = path.stat_json()
print(stat["downloadUri"])
print(stat["path"])

The reasoning is that stat() should keep a fixed, documented field set, the way pathlib.Path.stat() returns an os.stat_result — and growing the namedtuple means a new PR for every field JFrog adds. The accessor already had get_stat_json(); it just wasn't reachable without going through path._accessor.

Closing in favour of #504.