GrafanaRoute: Use React.Lazy instead of react-loadable and improve error handling (#55339)

* Things are working

* Add new GrafanaRoute tests

* removed old file

* Remove from package.json

package.json

@@ -146,7 +146,6 @@
     "@types/react-dom": "17.0.14",
     "@types/react-grid-layout": "1.3.2",
     "@types/react-highlight-words": "0.16.4",
-    "@types/react-loadable": "5.5.6",
     "@types/react-redux": "7.1.24",
     "@types/react-router-dom": "5.3.3",
     "@types/react-table": "7.7.12",
@@ -364,7 +363,6 @@
     "react-highlight-words": "0.18.0",
     "react-hook-form": "7.5.3",
     "react-inlinesvg": "3.0.0",
-    "react-loadable": "5.5.0",
     "react-moveable": "0.38.4",
     "react-popper": "2.3.0",
     "react-popper-tooltip": "4.4.2",