[C++] Refactor arrow/io/hdfs.h to use common FileSystem API

[asfimport]

As part of this refactor, the FileSystem-related classes in https://github.com/apache/arrow/blob/master/cpp/src/arrow/io/interfaces.h#L51 should be removed. The files should probably be moved also to arrow/filesystem

Reporter: Wes McKinney / @wesm

Related issues:

• [Python] Create FileSystem bindings (is blocked by)

PRs and other links:

• GitHub Pull Request #5709

_{Note: This issue was originally created as ARROW-6055. Please see the migration documentation for further details.}

[asfimport]

Ben Kietzman / @bkietz:
@wesm should io::FileSystem be deprecated or just deleted?

[asfimport]

Ben Kietzman / @bkietz:
In addition to removing io::FileSystem and io::FileStatistics, should HdfsPathInfo be replaced with fs::FileStats? It carries more information than fs::FileStats: last access time in addition to last modified time (though in seconds rather than ns since the epoch), block size, replication, and permissions. io-hdfs.pxi passes all of this for some_hdfs.ls(some_path, detail=True) but the docstring does not provide specifics about what metadata is guaranteed and test_hdfs.py doesn't even call ls(... detail=True)

[asfimport]

Wes McKinney / @wesm:
where do things stand on this?

[asfimport]

Wes McKinney / @wesm:
What is the latest here?

[asfimport]

Antoine Pitrou / @pitrou:
The old filesystem interfaces are not exposed in arrow/io/interfaces.h anymore. The new HDFS implementation still calls into the old one. It would be a welcome cleanup job to reintegrate all the HDFS filesystem code into arrow/filesystem/hdfs.cc, but rather low-priority.

[github-actions]

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