GH-73991: Split "Directory and file operations" section in shutil docs

[barneygale]

Split "Directory and file operations" section in five:

1. "Copying files"
2. "Recursively copying, moving and removing"
3. "Querying disk usage"
4. "Changing file ownership"
5. "Finding executables"

The "Platform-dependent efficient copy operations" information is moved to "Copying files". The examples of copytree() and rmtree() are moved into their function docs.

This should be slightly easier to navigate for users, and draws more of a distinction between the lower-level file copying functions and the higher-level copytree() / rmtree() / move() functions.

• Issue: Support moving across filesystems in pathlib.Path, as shutil.move() does #73991

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📚 Documentation preview 📚: https://cpython-previews--119159.org.readthedocs.build/

[pfmoore]

Taken in isolation, this example seems weird, as it's not actually ignoring anything. I'd suggest keeping the ignore_patterns example from the original text as well, and describe this example as something like:

You don't have to ignore anything, if you simply want to run some code for every directory that gets processed. For example, this snippet uses the ignore argument to add a logging call::

[pfmoore]

Apart from the one comment I made (I accidentally clicked "add a single comment" rather than "Start a review" 🙁) this LGTM

[barneygale]

Withdrawing this PR. With the work on GH-73991 at its end, we actually didn't need to touch shutil.