[Bugfix] Update grafana dashboard

[zhan9san]

Use templated datasource in query

FIX #6136 It defines a variable DS_PROMETHEUS. It should be used in the variable model_name but it does not.

Q: Why the metric vllm:num_requests_running is introduced? A: The label model_name is too common that node_exporter will also set this label to metrics. With a specific metric, it can ensure the metrics is vllm-related

Here is a negative example. See model_name="45N1767" in node_power_supply_info.

node_power_supply_info{capacity_level="Normal", env="build", exported_type="Battery", instance="example.com:9100", job="k8s", manufacturer="SANYO", model_name="45N1767", power_supply="BAT0", serial_number="3861", status="Not charging", team="build", technology="Li-ion", type="k8s"}

[github-actions[bot]]

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[github-actions[bot]]

This pull request has been automatically marked as stale because it has not had any activity within 90 days. It will be automatically closed if no further activity occurs within 30 days. Leave a comment if you feel this pull request should remain open. Thank you!

[mergify[bot]]

This pull request has merge conflicts that must be resolved before it can be merged. Please rebase the PR, @zhan9san.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

[github-actions[bot]]

This pull request has been automatically marked as stale because it has not had any activity within 90 days. It will be automatically closed if no further activity occurs within 30 days. Leave a comment if you feel this pull request should remain open. Thank you!