[OpenMP] [Flang] Add Fortran integer(kind=8) overloads for omp_lib APIs (#221451)

Fortran code that uses integer(8) arguments, including
-fdefault-integer-8, did not match omp_lib interfaces declared with
omp_integer_kind (typically kind 4). Added *_8 specific procedures to
named generic interfaces in omp_lib, exported matching Fortran and C
runtime entry points, and implemented the *_8 functions as thin wrappers
that saturate-convert arguments to 32-bit and call the existing APIs.

GitOrigin-RevId: 78f557806dca9c81453e94c038409fb9ad49d063