CLI: Rename --loglevel to --log-level for naming consistency

Other multi-word command line options use hyphens to separate
the words, so the --loglevel option introduced in CMake 3.15 was
inconsistent in this regard. Rename it to --log-level but still support
the original --loglevel name to preserve backward compatibility.
2 jobs for rename_loglevel_option
Status Name Job ID Coverage
  External
passed ghostflow-check-master

passed ghostflow-stager