MYRA npm RAT LD_PRELOAD persistence via .libcache.so and memfd_create

Detects persistence and fileless execution techniques associated with the MYRA Linux RAT. This includes monitoring for the creation of persistence files such as /usr/local/lib/.libcache.so for LD_PRELOAD hijacking and /etc/profile.d/.sh.local for shell-based persistence. It also monitors for suspicious process execution patterns where 'node' spawns a 'systemd-userdbd' masquerading process or invokes syscalls indicative of fileless execution, specifically memfd_create or fexecve.