Add new Portal Backend Sample Data API and remove Notifications API references (#1965)

* Fixed Sample Data logic and remove notifications references

* fixed undefined

* fixed unit tests

* fixed format test

* cleanup

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Co-authored-by: Asier Isayas <aisayas@microsoft.com>

src/Explorer/Controls/Settings/SettingsComponent.test.tsx

@@ -134,7 +134,6 @@ describe("SettingsComponent", () => {
       readSettings: undefined,
       onSettingsClick: undefined,
       loadOffer: undefined,
-      getPendingThroughputSplitNotification: undefined,
     } as ViewModels.Database;
     newCollection.getDatabase = () => newDatabase;
     newCollection.offer = ko.observable(undefined);