[BUG] Consul instance watch task can stop after one polling error

### Current Behavior

Consul instance watch tasks can stop after a transient Consul error.

`ConsulInstanceRegisterRepository.watcherStart()` schedules `watchConfigKeyValues(selectKey)` with `scheduleWithFixedDelay(...)`:

```java
watchFutures.add(this.executor.scheduleWithFixedDelay(
() -> this.watchConfigKeyValues(selectKey), 5, Integer.parseInt(watchDelay), TimeUnit.SECONDS));
```

`watchConfigKeyValues()` calls `getHealthServices(...)`, which performs the Consul blocking query. Neither the scheduled lambda nor `watchConfigKeyValues()` catches exceptions. If the Consul request fails, the exception escapes the fixed-delay task and later executions are suppressed by the scheduler.

### Expected Behavior

A failed Consul watch poll should be logged and retried on the next delay interval.

### Impact

After one transient Consul watch failure, the local `watcherInstanceRegisterMap` may stop receiving instance updates for that select key until the process restarts or the watch is re-created.

### Code Location

- `shenyu-registry/shenyu-registry-consul/src/main/java/org/apache/shenyu/registry/consul/ConsulInstanceRegisterRepository.java`
- `watcherStart()` schedules the fixed-delay watch task.
- `watchConfigKeyValues()` and `getHealthServices()` allow exceptions from Consul calls to escape.

Read shenyu-registry/shenyu-registry-consul/src/main/java/org/apache/shenyu/registry/consul/ConsulInstanceRegisterRepository.java, starting with watcherStart(), watchConfigKeyValues(), and getHealthServices(). Confirm how scheduleWithFixedDelay handles an escaping exception, then verify that a failed Consul poll is logged and the same watch runs again after the next delay interval.

Written by the indexing model from the issue text.