[libc] Add chown and getgid implementations (#166434)

Implements chown and getgid per the POSIX specification and adds
corresponding unit tests. getgid is added as it is required by the chown
unit tests. This PR will address #165785

Co-authored-by: shubh@DOE <shubhp@mbm3a24.local>
GitOrigin-RevId: 0fd029858a819dfbc5e4ec18d456d055359b0317