enhancement(notifications): remove from state after dismissal

This commit changes the implementation from an array to a Map,
as that makes accessing a notification for dismissal or removal
more performant.

Signed-off-by: Erik Michelson <github@erik.michelson.eu>

frontend/src/test-utils/mock-ui-notifications.ts

@@ -14,6 +14,7 @@ export const mockUiNotifications = () => {
   jest.spyOn(useUiNotificationsModule, 'useUiNotifications').mockReturnValue({
     showErrorNotification: jest.fn(),
     dismissNotification: jest.fn(),
-    dispatchUiNotification: jest.fn()
+    dispatchUiNotification: jest.fn(),
+    pruneNotification: jest.fn()
   })
 }