add workflow labels to metrics?

# Summary

add workflow labels to the metric?

# Use Cases

When I have two workflowTemplates (A,B), I want to know the overall situation of workflow of A and B respectively. The current metric does not support me to do this. Since there is no label for workflow.

NOW:
```
argo_workflows_count{container="workflow-controller", endpoint="metrics",
instance="127.0.0.1:9090", job="workflow-controller-metrics", namespace="argo",
pod="workflow-controller-7d69c4b564-t6xn8",
service="workflow-controller-metrics", status="Error"}
```

BETTER:
```
argo_workflows_count{container="workflow-controller", endpoint="metrics",
instance="127.0.0.1:9090", job="workflow-controller-metrics", namespace="argo",
pod="workflow-controller-7d69c4b564-t6xn8",
service="workflow-controller-metrics", status="Error",labelName="LabelValue"}
```

---

**Message from the maintainers**:

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Start at the workflow-controller metrics entry point and inspect how argo_workflows_count is currently emitted and how workflow templates are identified. Clarify which workflow label and value should be exposed, including acceptable cardinality, then add coverage for separate templates A and B and verify the metric output includes the agreed label.

Written by the indexing model from the issue text.