Test plugins: Add datasource test plugin with field tests (#95472)

* add new test plugin

* add some field validation tests

* update lockfile

* fix bad test file name

e2e/test-plugins/grafana-test-datasource/module.ts

@@ -0,0 +1,9 @@
+import { DataSourcePlugin } from '@grafana/data';
+import { DataSource } from './datasource';
+import { ConfigEditor } from './components/ConfigEditor';
+import { QueryEditor } from './components/QueryEditor';
+import { MyQuery, MyDataSourceOptions } from './types';
+
+export const plugin = new DataSourcePlugin<DataSource, MyQuery, MyDataSourceOptions>(DataSource)
+  .setConfigEditor(ConfigEditor)
+  .setQueryEditor(QueryEditor);