fix(proxy-wasm) load filter from lua - WasmX as module

When WasmX is compiled as shared library and loaded into Nginx via
`load_module`, its modules will end up after `ngx_http_lua_module` in
`ngx_cycle->modules` list.

As a result, `ngx_http_lua_init_worker_by_inline` -- which might try to
load wasm filters -- is called before `ngx_wasm_core_init_process` -- which
prepares a wasm vm -- is ever called, causing the load to fail.

src/wasm/ngx_wasm_core_module.c

@@ -270,6 +270,38 @@ ngx_wasm_core_create_conf(ngx_conf_t *cf)
     static const ngx_str_t   runtime_name = ngx_string(NGX_WASM_RUNTIME);
     static const ngx_str_t   ip = ngx_string(NGX_WASM_DEFAULT_RESOLVER_IP);
 
+#if (NGX_WASM_LUA)
+    ngx_uint_t               lua_i, wasm_i, tmp_i;
+    ngx_module_t            *lua_module = NULL; *wasm_module = NULL, *tmp;
+
+    for (lua_i = 0; cycle->modules[lua_i]; lua_i++) {
+        lua_module = cycle->modules[lua_i];
+        if (ngx_strcmp(lua_module->name, "ngx_http_lua_module") == 0) {
+            break;
+        }
+    }
+
+    for (wasm_i = lua_i + 1; cycle->modules[wasm_i]; wasm_i++) {
+        wasm_module = cycle->modules[wasm_i];
+        if (ngx_strcmp(wasm_module->name, "ngx_wasm_core_module") == 0) {
+            break;
+        }
+    }
+
+    /* cycle->modules[wasm_i] is NULL if execution order has been rectified */
+    if (cycle->modules[wasm_i] && cycle->modules[lua_i]) {
+        tmp = cycle->modules[lua_i];
+        tmp_i = cycle->modules[lua_i]->index;
+
+        cycle->modules[lua_i]->index = cycle->modules[wasm_i]->index;
+        cycle->modules[wasm_i]->index = tmp_i;
+
+        cycle->modules[lua_i] = cycle->modules[wasm_i];
+        cycle->modules[wasm_i] = tmp;
+
+    }
+#endif
+
     wcf = ngx_pcalloc(cycle->pool, sizeof(ngx_wasm_core_conf_t));
     if (wcf == NULL) {
         return NULL;