GH-73991: Add follow_symlinks argument to `pathlib.Path.copy()` (#120519)

Add support for not following symlinks in `pathlib.Path.copy()`.

On Windows we add the `COPY_FILE_COPY_SYMLINK` flag is following symlinks is disabled. If the source is symlink to a directory, this call will fail with `ERROR_ACCESS_DENIED`. In this case we add `COPY_FILE_DIRECTORY` to the flags and retry. This can fail on old Windowses, which we note in the docs.

No news as `copy()` was only just added.