Rename configuration variables and functions to reflect broader
functionality beyond just log files. Updates include renaming
LOG_DIRS_FOR_CLEANUP to DIRS_FOR_AUTODELETE and
clean_log_files to clean_directory_files. Adds safety warnings
to prevent deletion of critical HANA system logs.
BREAKING CHANGE: Config keys renamed from LOG_DIRS_FOR_CLEANUP to
DIRS_FOR_AUTODELETE and MAX_LOG_FILE_AGE_DAYS to MAX_FILE_AGE_DAYS
