load-path: Avoid using file_stat on Windows (bug #59711). * liboctave/system/oct-time.h, oct-time.cc (octave::sys::file_time): New class to handle an efficient native file time type per platform. * libinterp/corefcn/load-path.h (load_path::dir_info::dir_mtime, load_path::dir_info::dir_time_last_checked): Change type to new class. * libinterp/corefcn/load-path.cc (subdirs_modified, load_path::dir_info::update, load_path::dir_info::initialize): Avoid using file_stat on Windows.