[Bug] Use Nacos as registry center, every diffrent registry.group eatablished it's own NamingService connection, that causes too many connections to be established

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### Search before asking

- [x] I had searched in the [issues](https://github.com/apache/dubbo/issues?q=is%3Aissue) and found no similar issues.

### Apache Dubbo Component

Java SDK (apache/dubbo)

### Dubbo Version

Dubbo Java 3.2.13, JDK 8, Mac OS/Linux

### Steps to reproduce this issue

In one Dubbo project use Nacos as registry center, there are several interfaces, and set different `registry.group` for each interface, that will established one connection to Nacos for each interface(registry.group), so it causes too many connections to be established.

I check the code in class `org.apache.dubbo.registry.nacos.NacosRegistryFactory`, in the method `createRegistry` will create a `NamingService` every time.

***Is it neccessary to create a new `NamingService` every time for each different `registry.group` ?***

some related code:

### What you expected to happen

Establish only one NamingService Connection for each `Nacos Host`，not for each `registry.group`

### Anything else

_No response_

### Are you willing to submit a pull request to fix on your own?

- [x] Yes I am willing to submit a pull request on my own!

### Code of Conduct

- [x] I agree to follow this project's [Code of Conduct](https://www.apache.org/foundation/policies/conduct)

Start at org.apache.dubbo.registry.nacos.NacosRegistryFactory#createRegistry and inspect the related Nacos registry code shown in the issue, comparing behavior across registry.group values. Reproduce the case with several interfaces and groups; done means one NamingService connection per Nacos host rather than one per registry.group, with relevant regression coverage if available.

Written by the indexing model from the issue text.