Use @grafana/toolkit to manage build

[ryantxu]

this PR tries to use the new toolkit to build a robust existing app.

FYI -- this includes a LOT of changes, but most of that is deleting dist and autofixes. When toolkit can build this succesfully, I will drop this PR and make a few smaller ones

[ryantxu]

@dprokop Any idea why it can't find 'app/plugins/sdk'?

[torkelo]

probably not found because of missing interface exports here:

https://github.com/grafana/grafana-sdk-mocks/tree/master/app/features/panel