Use full precision for Eigen matrix output (fmt/spdlog)
This MR changes the output precision for Eigen matrices/vectors for fmt/spdlog.
Such output is used, e.g., with debug output of local matrices. To test set the necessary environment variables, e.g.:
OGS_LOCAL_MAT_OUT_PREFIX=/tmp/test_precision_ OGS_LOCAL_MAT_OUT_ELEMENTS=0 /path/to/ogs /path/to/project.prj