Test cases to avoid panel missing in Grafana

[flowbehappy]

Feature Request

Is your feature request related to a problem? Please describe:
Like this issue, #1083, tiup's cluster failed to add TiFlash nodes to Grafana's Node_exporter panel. And currently, we don't have test cases to cover this issue.

Describe the feature you'd like:

Test cases that promise we don't lose any components' panels in Grafana.

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy:

[AstroProfundis]

Grafana panels are maintained by each component themselves, we need to find a way to know which files are "correct" to be packaged into the tar ball when we publish new releases.