[3.12] GH-119054: Add "Renaming and deleting" section to pathlib docs. (GH-120465) (#120473)

GH-119054: Add "Renaming and deleting" section to pathlib docs. (GH-120465)

Add dedicated subsection for `pathlib.Path.rename()`, `replace()`,
`unlink()` and `rmdir()`.
(cherry picked from commit d88a1f2e156cd1072119afa91d4f4dc4037c1b21)

Co-authored-by: Barney Gale <barney.gale@gmail.com>