Add all `prif` interfaces from latest design doc draft (revision 0.2)

[ktras]

• [ ] Add all subroutines
• [ ] Add all constants from iso_fortran_env module
• [ ] After iso_fortran_env module constants are added, remove any use-stmts for iso_fortran_env and replace references to those constants with the corresponding prif constants
• [ ] Add test that invokes all of the prif symbols so that the link time errors will occur if something from prif is missing from Caffeine

[bonachea]

This notably includes all of "2.3.2 Constants in ISO_FORTRAN_ENV", which currently all appear to be missing from the implementation

[bonachea]

subsumed by #119