refactor: Remove LabelingFlow/ContextMenu services and reimplement on top of the Dialog service #1264 (#1292)

* Remove ContextMenu and Labelling services and provider to use DialogService directly

* Refactor init to display labelling

* Cleanup labelling flow in measurements init

* Cleanup viewer imports

* Add classname to toolcontextmenu

* Add error message

platform/ui/src/components/index.js

@@ -17,6 +17,7 @@ import { RoundedButtonGroup } from './roundedButtonGroup';
 import { SelectTree } from './selectTree';
 import { SimpleDialog } from './simpleDialog';
 import { OHIFModal } from './ohifModal';
+import { ContextMenu } from './contextMenu';
 import {
   PageToolbar,
   StudyList,
@@ -27,6 +28,7 @@ import { ToolbarSection } from './toolbarSection';
 import { Tooltip } from './tooltip';
 
 export {
+  ContextMenu,
   Checkbox,
   CineDialog,
   ViewportDownloadForm,