Pedantic: use of C VLAs is forbidden by ISO C++

[program--]

utilities/parallel_utils.h makes use of C VLAs in at least 6 places, as outputted by GCC 13.2.1.

An expedient solution would be to replace VLAs with std::vector.

In file included from src/NGen.cpp:51:
include/utilities/parallel_utils.h: In function ‘void parallel::get_hosts_array(int, int, int*)’:
include/utilities/parallel_utils.h:161:13: error: ISO C++ forbids variable length array ‘actualHostnameCStrLength’ [-Wvla]
  161 |         int actualHostnameCStrLength[mpi_num_procs];
      |             ^~~~~~~~~~~~~~~~~~~~~~~~
include/utilities/parallel_utils.h:178:13: error: ISO C++ forbids variable length array ‘recvDisplacements’ [-Wvla]
  178 |         int recvDisplacements[mpi_num_procs];
      |             ^~~~~~~~~~~~~~~~~
include/utilities/parallel_utils.h:190:14: error: ISO C++ forbids variable length array ‘hostnames’ [-Wvla]
  190 |         char hostnames[totalLength];
      |              ^~~~~~~~~
include/utilities/parallel_utils.h: In function ‘bool parallel::mpi_send_text_file(const char*, int, int)’:
include/utilities/parallel_utils.h:243:14: error: ISO C++ forbids variable length array ‘buf’ [-Wvla]
  243 |         char buf[bufSize];
      |              ^~~
include/utilities/parallel_utils.h: In function ‘bool parallel::mpi_recv_text_file(const char*, int, int)’:
include/utilities/parallel_utils.h:332:14: error: ISO C++ forbids variable length array ‘buf’ [-Wvla]
  332 |         char buf[bufSize];
      |              ^~~
include/utilities/parallel_utils.h: In function ‘bool parallel::subdivide_hydrofabric(int, int, const std::string&, const std::string&, const std::string&)’:
include/utilities/parallel_utils.h:525:17: error: ISO C++ forbids variable length array ‘hostIdForRank’ [-Wvla]
  525 |             int hostIdForRank[mpi_num_procs];
      |                 ^~~~~~~~~~~~~