[Doc][Python] Better document the new pa.fs.HadoopFileSystem

In order to deprecate the "legacy" pa.hdfs.HadoopFileSystem and pa.hdfs.connect(), we should ensure that the documentation for the new filesystem interface is fully up to date:

• The docstring of pyarrow.fs.HadoopFileSystem misses some keywords (that are included in the docstring of pa.hdfs.HaddopFileSystem)
• The user guide about the legacy one (https://arrow.apache.org/docs/python/filesystems_deprecated.html) contains more content, which should be added to the new user guide page as well (if still correct for the new filesystem)