Chore: Migrate E2E tests to grafana/plugin-e2e

[mckn]

Description

This is an "epic" issue where we track the progress of the migration from @grafana/e2e and @grafana/e2e-selectors to the new and shiny @grafana/plugin-e2e package.

Todo

• [x] https://github.com/grafana/grafana-plugin-examples/pull/251
• [x] https://github.com/grafana/grafana-plugin-examples/pull/252
• [ ] app-with-dashboards
• [ ] app-with-extension-point
• [ ] app-with-extensions
• [ ] app-with-on-behalf-of-auth
• [ ] app-with-scenes
• [ ] app-with-service-account
• [ ] datasource-basic
• [ ] datasource-http-backend
• [ ] datasource-http
• [ ] datasource-logs
• [ ] datasource-streaming-backend-websocket
• [ ] datasource-streaming-websocket
• [ ] panel-basic
• [ ] panel-datalinks

[sunker]

Fixed in https://github.com/grafana/grafana-plugin-examples/pull/272