Able to query `pd-ctl scheduler config <scheduler>` on dashboard

[aylei]

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Feature Request

Is your feature request related to a problem? Please describe:

Sometimes users need to inspect the scheduler config, and dashboard would be more easy to use then pd-ctl

Describe the feature you'd like: Able to query pd-ctl scheduler config <scheduler> on dashboard, like other PD APIs.

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy:

[breezewish]

Thanks for the report! Can they be covered by pd-ctl config show all?