GH-130614: Add test suites for readable and writable pathlib paths

[barneygale]

Add test.test_pathlib.test_read, which tests ReadablePath subclasses. Tests are run against ReadableZipPath, ReadableLocalPath, and Path. This test suite is mostly incomplete.

Add test.test_pathlib.test_write, which tests WritablePath subclasses. Tests are run against WritableZipPath, WritableLocalPath, and Path. This test suite is mostly complete.

Add test.test_pathlib.support.zip_path, which provides the *ZipPath classes mentioned above. It also provides a ZipPathGround class that's used by tests to make assertions about the contents of the zip file.

Add test.test_pathlib.support.local_path, which provides the *LocalPath classes mentioned above. They're stripped-back versions of pathlib.Path, basically. It also provides LocalPathGround class that's used by tests to access the local filesystem.

• Issue: Parametrize tests for pathlib.Path.copy() #130614

[barneygale]

@srinivasreddy here's a framework for copy tests - see test_copy.py. There a bunch more copying tests in test_pathlib_abc that will need to be ported to the new framework, if you'd like to have a go :)

[srinivasreddy]

@barneygale You have made significant progress, i do not think it would be right for me to start working on this. I will find something else to work on. Thanks 🙏🏾

[barneygale]

Closing this PR - I've split it into several other PRs attached to the same issue.