emulators/linux_base-rl9: integrate devel/linux-rl9-libsigsegv into linux_base (+)

[g]awk and grep utilities depends on libsigsegv.so.2.0.6
Integrate devel/linux-rl9-libsigsegv into the emulators/linux_base-rl9 package
to resolve missed dependency
Drop dedicated devel/linux-rl9-libsigsegv port
Bump all linux-rl9-libsigsegv consumers to track changed dependency

PR: 286032