Refactor: libpe_status: separate digest-related code into own file
    
    There are no changes in the code.
    
    Before:
      4035 lib/pengine/unpack.c
      2966 lib/pengine/utils.c
      7001 total
    
    After:
       509 lib/pengine/pe_digest.c
      4008 lib/pengine/unpack.c
      2502 lib/pengine/utils.c
      7019 total