Variables: replaces homegrown variableAdapters with Registry (#22866)

* Refactor: intial commit

* Tests: fixes tests

* Refactor: adds stricter typings

public/app/features/variables/datasource/actions.test.ts

@@ -18,7 +18,7 @@ import { changeVariableEditorExtended } from '../editor/reducer';
 import { datasourceBuilder } from '../shared/testing/builders';
 
 describe('data source actions', () => {
-  variableAdapters.set('datasource', createDataSourceVariableAdapter());
+  variableAdapters.setInit(() => [createDataSourceVariableAdapter()]);
 
   describe('when updateDataSourceVariableOptions is dispatched', () => {
     describe('and there is no regex', () => {

public/app/features/variables/datasource/adapter.ts

@@ -11,8 +11,9 @@ import { updateDataSourceVariableOptions } from './actions';
 
 export const createDataSourceVariableAdapter = (): VariableAdapter<DataSourceVariableModel> => {
   return {
+    id: 'datasource',
     description: 'Enabled you to dynamically switch the datasource for multiple panels',
-    label: 'Datasource',
+    name: 'Datasource',
     initialState: initialDataSourceVariableModelState,
     reducer: dataSourceVariableReducer,
     picker: OptionsPicker,