MetricsSubscriber subscribe more than once

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

### Ⅰ. Issue Description


### Ⅱ. Describe what happened

If there is an exception, please attach the exception trace:

```
Just paste your stack trace here!
```

### Ⅲ. Describe what you expected to happen

### Ⅳ. How to reproduce it (as minimally and precisely as possible)

1. xxx
2. xxx
3. xxx

### Ⅴ. Anything else we need to know?

### Ⅵ. Environment:

- JDK version :
- OS :
- Others:

The issue identifies MetricsSubscriber and reports that it subscribes more than once, but provides no reproduction steps, expected behavior, files, or tests. Start by finding the MetricsSubscriber implementation and establishing a minimal reproduction of duplicate subscription; done means the behavior is reproduced, the intended subscription count is confirmed, and a regression test verifies it.

Written by the indexing model from the issue text.