monitoring: create uniform variables API for dashboards
Created by: bobheadxi
Creates a uniform Variables
API, ContainerVariable
, that abstracts away a lot of the behind-the-scenes dashboard config and potential gotchas to make it easier to define template variables on dashboards. API docs: https://sourcegraph.com/github.com/sourcegraph/sourcegraph@monitoring/variables-api/-/docs/monitoring/monitoring?ContainerVariable
Poked around with the local dev instructions and the dashboards still work correctly I think, and also updated the dev instructions to use sg
Closes https://github.com/sourcegraph/sourcegraph/issues/29416