[3.12] pythonGH-119054: Add "Querying file type and status" section t…

…o pathlib docs (pythonGH-119055)

Add a dedicated subsection for `Path.stat()`-related methods, specifically
`stat()`, `lstat()`, `exists()`, `is_*()`, and `samefile()`..
(cherry picked from commit 81d6336)

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