gh-109613: _pystat_fromstructstat() checks for exceptions (#109618)

Fix os.stat() and os.DirEntry.stat(): check for exceptions.
Previously, on Python built in debug mode, these functions could
trigger a fatal Python error (and abort the process) when a function
succeeded with an exception set.

_pystat_fromstructstat() now exits immediately if an exception is
raised, rather only checking for exceptions at the end. It fix
following fatal error in fill_time():

    Fatal Python error: _Py_CheckSlotResult:
    Slot * of type int succeeded with an exception set