pathlib docs: table of corresponding os/os.path functions is disorganised

[barneygale]

Documentation

The Corresponding tools table in the pathlib docs has evolved organically and is overdue some editing.

Linked PRs

• GH-121462: pathlib docs: improve table of corresponding os/os.path functions #121465
• [3.13] GH-121462: pathlib docs: improve table of corresponding os/os.path functions (GH-121465) #122359
• [3.12] GH-121462: pathlib docs: improve table of corresponding os/os.path functions (GH-121465) #122360