[libc] Implement pathconf/fpathconf

[SchrodingerZhu]

Provide portable way to get NAME_MAX or PATH_MAX. See also https://man7.org/linux/man-pages/man3/pathconf.3.html.

• [ ] pathconf/fpathconf

These function itself may need:

• [x] #85964

This will also deliver the following functions along the way:

• [ ] statvfs/fstatvfs (POSIX API)

[robincaloudis]

@SchrodingerZhu, are you already working on it? Otherwise, I'd give it a shot.

[SchrodingerZhu]

Hi, the statvfs/fstatvfs part is already in progress. After that, you can look into the pathconf and fpathconf part if you want.

You can check the design in bionic libc.