design how to verify scheduler working well in Schrodinger

[siddontang]

We have many test cases in Schrodinger which verify our data can't be broken, corrupted, but now we have no way to verify PD scheduler can work as expected, E.g, if a PD can't send schedule command to TiKV, we should detect this and alert us.

So I think we also need to figure out a way to verify the scheduler, alert through metrics and deploy it in Schrodinger.