Refactor: Plugin exports & data source / panel types (#16364)

* wip: began work off removing meta and pluginExports from DataSourceApi interface

* WIP: changing how plugins are exports and loaded

* Down the refactoring rabit hole that keeps expanding

* TestData now returns DataSourcePlugin

* Refactoring: fixed app config page loading, type renamings and more typings

* Refactor: Correct casing on DatasourceStatus => DataSourceStatus

public/app/features/datasources/state/navModel.ts

@@ -84,6 +84,8 @@ export function getDataSourceLoadingNav(pageName: string): NavModel {
         version: '',
       },
       includes: [{ type: '', name: '', path: '' }],
+      module: '',
+      baseUrl: '',
     }
   );