dubbo 2.7升级到dubbo 3.0后泛化调用的注册中心配置被覆盖的问题

- [ ] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.

## 之前dubbo 2.7泛化调用的时候，注册中心地址是开放给用户输入的referenceConfig.setRegistry，类似下面这种
`

ReferenceConfig referenceConfig = new ReferenceConfig<>();
referenceConfig.setInterface("com.demo.test");
referenceConfig.setTimeout(2000000);
referenceConfig.setRetries(0);
referenceConfig.setRegistry(new RegistryConfig("zookeeper://127.0.0.1"));
referenceConfig.setGeneric("true");
referenceConfig.setTimeout(7000);
GenericService genericService = referenceConfig.get();
Map map = new HashMap<>();
Object result = genericService.$invoke("captcha", new String[]{"com.base.Req"}, new Object[]{map});
System.out.println("captcha(return):"+result);`

> 将dubbo升级到3.0.10后，这个referenceConfig.setRegistry用户输入的值无效，会在运行的时候被替换成应用本身的注册中心地址，所以想问下，dubbo3.0.10后泛化调用不再支持这些注册中心参数开放给用户了？需要在应用的配置源里定义好多个注册中心的id，让用户只能选择匹配的registryId去做关联才行吗

Start by reproducing the provided GenericService example on Dubbo 3.0.10 and compare the configured registry with the application's registry address at runtime. Trace how ReferenceConfig.setRegistry is resolved and identify whether the behavior is an intentional configuration rule or a regression. Done means the supported registry configuration behavior and any required change are verified.

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