SafeDynamicImport: Updates so that it does not act as an ErrorBoundary (#20170)

* SafeDynamicImport: Fixes so that it shows different messages depending on error

* Refactor: Fixes type error

* Refactor: Adds grafana constant to error message

* Refactor: Renames components and adds exports

* Refactor: Uses react-loader instead

* Refactor: Updates after PR comments

* Tests: Adds tests for loadComponentHandler

package.json

@@ -198,6 +198,7 @@
     "@babel/polyfill": "7.6.0",
     "@grafana/slate-react": "0.22.9-grafana",
     "@torkelo/react-select": "2.4.1",
+    "@types/react-loadable": "5.5.2",
     "angular": "1.6.9",
     "angular-bindonce": "0.3.1",
     "angular-native-dragdrop": "1.2.2",
@@ -234,6 +235,7 @@
     "react-dom": "16.8.6",
     "react-grid-layout": "0.16.6",
     "react-highlight-words": "0.11.0",
+    "react-loadable": "5.5.0",
     "react-popper": "1.3.3",
     "react-redux": "7.1.1",
     "react-sizeme": "2.5.2",