在 instrument-lib/ 里，需要支持define 工具类

比如在增强 dubbo里，可能会有一些工具类，处理数据之后，才能传送到后续处理函数里。那么这些工具类需要在运行时动态 define 到应用的 ClassLoader 里。

Start by inspecting the instrument-lib/ directory and its existing runtime class-loading or instrumentation entry points. Determine how utility classes needed by enhanced Dubbo processing should be dynamically defined in the application ClassLoader. Done means the supported utility classes can be defined there and used by subsequent processing functions, with tests covering the behavior.

Written by the indexing model from the issue text.