Otherwise, this query will produce warning message per each
healthcheck, telling the user:
```
WARN <...> - Aggregation query used without partition key
```
We need to reverse the dependency of `emqx_bridge` and `emqx_bridge_*`, because the former
loads and starts bridges during its application startup. If the individual bridge
application being loaded has not started with its dependencies, the supervision tree will
not be ready for that.