`exec_run` and `exec_kast` take `save_directory` argument but the corresponding commands don't have those options

[nwatson22]

exec_run and exec_kast take save_directory argument but the corresponding commands don't have --save-directory options. This becomes a problem because KEVM is using save_directory to save its temp files, and deleting them if none is specified. The user might want to specify a directory to keep these for debugging. We should either enable --save-directory for these commands while making clearer in the help message that it is not just for storing CFGs, or make this a separate directory option.