ast_coredumper: check ast_debug_tools.conf permissions

ast_coredumper: check ast_debug_tools.conf permissions

Prevent ast_coredumper from using ast_debug_tools.conf files that are
not owned by root or are writable by other users or groups.

Prevent ast_logescalator and ast_loggrabber from doing the same if
they are run as root.

Resolves: #GHSA-rvch-3jmx-3jf3

UserNote: ast_debug_tools.conf must be owned by root and not be
writable by other users or groups to be used by ast_coredumper or
by ast_logescalator or ast_loggrabber when run as root.