* Extract DatasourceVariableForm logic and use it in core grafana
* Implement DataSourceVariable editor in scenes
* Refactor VariableSelect and add unit test for DataSourceVariableEditor
* Refactor old unit test to use userEvent and mock getDataSourceSrv
* refactor(selectoptiontest): move helper function out of grafana/ui so testing-lib isn't in bundle
* test(selectoptionintest): update import location of helper function
* test(amroutes): put back missing selectOptionInTest helper
* test(selectoptionintest): clean up remaining file imports / exports
* test(queryeditor): fix failing import
* refactor(grafana-ui): reuse selectOptionInTest in SelectBase test
* Narrow Variable editor state using selector functions
- Explicitly type "extended" editor state in editor/reducter.ts using a union
- Create selectors to narrow the types, using unique properties from each extended state to discriminate the union
- Update DataSourceVariableEditor to use new style of redux connector
- Update variable editor components to use new selectors
* fix tests
* Make adhoc variable infoText optional, because it is!
* Add AdHocVariableEditor tests
* DataSourceVariableEditor tests
* comment
* reset
* Wrote tests for selectors \(that actually caught a bug, whodathunkit)
* fix stray types and lint issues
* Rename selector functions
