Add wasm-mutator-fuzz test (#3420)

tests/fuzz/wasm-mutator-fuzz/portal/nginx.conf

@@ -0,0 +1,15 @@
+error_log stderr;
+
+pid /var/run/nginx.pid;
+
+events {
+  worker_connections 1024;
+}
+
+http {
+  access_log /dev/stdout;
+  server_tokens off;
+
+  include /etc/nginx/mime.types;
+  include /etc/nginx/conf.d/*.conf;
+}