Sandbox: Add basic e2e tests for datasources inside sandbox (#76226)

* Sandbox: initial dummy datasource plugin for e2e

* WIP: tests

* Add metrics to plugin.json so it shows up in explore

* Fix false positives in frontend-sandbox-datasource.spec.ts

* Change typed name to be static

* Add code to delete the datasource after tests are complete

* Add fail on status code

* Update tests for more config

* Replace visit with existing page

* Delete cleanup code

e2e/custom-plugins/frontend-sandbox-datasource-test/plugin.json

@@ -0,0 +1,26 @@
+{
+  "$schema": "https://raw.githubusercontent.com/grafana/grafana/master/docs/sources/developers/plugins/plugin.schema.json",
+  "type": "datasource",
+  "name": "Sandbox datasource test plugin",
+  "id": "sandbox-test-datasource",
+  "metrics": true,
+  "info": {
+    "keywords": ["explore", "datasource"],
+    "description": "",
+    "author": {
+      "name": "Grafana"
+    },
+    "logos": {
+      "small": "img/logo.svg",
+      "large": "img/logo.svg"
+    },
+    "links": [],
+    "screenshots": [],
+    "version": "1.0.0",
+    "updated": "2023-06-27"
+  },
+  "dependencies": {
+    "grafanaDependency": ">=10.0",
+    "plugins": []
+  }
+}