@grafana/e2e: improvements (#25497)

* Minor changes

* Use UI for removing dashboards and datasources

… with an optional “quick” mode that instead does so via a request

* Improved URL helpers

* Simplified test teardown

* Added support for multiple tests

... instead of being forced to cram everything into a single test because the session was cleared

packages/grafana-e2e/cypress/plugins/extendConfig.js

@@ -15,6 +15,7 @@ module.exports = async baseConfig => {
     // @todo: https://github.com/cypress-io/cypress/issues/6406
     const jsonReporter = require.resolve('@mochajs/json-file-reporter');
 
+    // @todo `baseUrl: env.CYPRESS_BASEURL`
     const projectConfig = {
       fixturesFolder: `${CWD}/cypress/fixtures`,
       integrationFolder: `${CWD}/cypress/integration`,