Protected-file disclosure via inverted ktrace privilege check

Information disclosure in FreeBSD 13.3, 14.0, and 14.1 allows local users to read protected files by tracing setuid programs. In ktrprocexec, an inverted priv_check_cred result causes the kernel to retain ktrace parameters when a traced process executes a setuid binary. An unprivileged local user must start tracing before that execution and can then inspect privileged file reads, including the local password database.