silo: add "hzip" and "fzip" variants (#23447)
silo: add "hzip" and "fzip" variants (#23447)

SILO has optional support for compression libraries that require 
C++ (hzip and fpzip). This patch exposes those options as variants
to enable configuration of SILO without the C++ libraries for C 
applications. hzip and fpzip are enabled by default to preserve 
current behavior.
LLNL/spack,LLNL/spack,LLNL/spack,LLNL/spack,LLNL/spack