[3.12] GH-120794: Use example paths with multiple parts in pathlib docs (GH-122887) (#122896)

GH-120794: Use example paths with multiple parts in pathlib docs (GH-122887)

In the documentation of `PosixPath` and `WindowsPath`, and their `Pure*`
equivalents, use example paths with multiple non-anchor parts.

(cherry picked from commit 363374cf69a7e2292fe3f1c6bedd199088958cc2)

Co-authored-by: Barney Gale <barney.gale@gmail.com>
Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>