[BUG] fallbackUri issue

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

fallback config:

when fallback is triggered, the `ip:port` info is missing from the fallback request.

From the current code, it appears that this `fallbackUri` field supports two configuration methods(eg. `fallback:/far/boo` or `http://ip:port/far/boo`). Does this align with our expectations?

### Expected Behavior

_No response_

### Steps To Reproduce

_No response_

### Environment

```markdown
ShenYu version(s): 2.6
```

### Debug logs

_No response_

### Anything else?

_No response_

Start by tracing how the fallbackUri configuration is handled in ShenYu 2.6, comparing the fallback:/far/boo and http://ip:port/far/boo forms shown in the issue. Reproduce the fallback request and determine the expected handling of the missing ip:port; done means the behavior is corrected and the expected fallback URI semantics are documented or covered by an appropriate test.

Written by the indexing model from the issue text.