Refactor sepolicy.rules resolve

We resolve available partitions for sepolicy.rules when patching
boot and bind mount the partition by magiskinit.

For older devices, the previous logic won't work because the part name
is never readable.

Co-authored-by: topjohnwu <topjohnwu@gmail.com>

native/src/init/init.cpp

@@ -83,6 +83,9 @@ int main(int argc, char *argv[]) {
     if (name == "magisk"sv)
         return magisk_proxy_main(argc, argv);
 
+    if (name == "magiskinit"sv && argc == 2 && argv[1] == "--rules-device"sv)
+        return rust::print_rules_device();
+
     if (getpid() != 1)
         return 1;