config: 添加用户配置加载流程和默认配置

src/config/runtime_config.h

@@ -0,0 +1,6 @@
+#pragma once
+
+typedef struct runtime_init_desc_t runtime_init_desc_t;
+
+bool runtime_config_load(const char *override_path, runtime_init_desc_t *out);
+void runtime_config_cleanup(runtime_init_desc_t *desc);