feat(grid): remove viewportIndex and only rely on viewportId (#3591)

Co-authored-by: Bill Wallace <wayfarer3130@gmail.com>

extensions/measurement-tracking/src/contexts/TrackedMeasurementsContext/promptBeginTracking.js

@@ -10,24 +10,24 @@ const RESPONSE = {
 
 function promptBeginTracking({ servicesManager, extensionManager }, ctx, evt) {
   const { uiViewportDialogService } = servicesManager.services;
-  const { viewportIndex, StudyInstanceUID, SeriesInstanceUID } = evt;
+  const { viewportId, StudyInstanceUID, SeriesInstanceUID } = evt;
 
   return new Promise(async function(resolve, reject) {
     let promptResult = await _askTrackMeasurements(
       uiViewportDialogService,
-      viewportIndex
+      viewportId
     );
 
     resolve({
       userResponse: promptResult,
       StudyInstanceUID,
       SeriesInstanceUID,
-      viewportIndex,
+      viewportId,
     });
   });
 }
 
-function _askTrackMeasurements(uiViewportDialogService, viewportIndex) {
+function _askTrackMeasurements(uiViewportDialogService, viewportId) {
   return new Promise(function(resolve, reject) {
     const message = 'Track measurements for this series?';
     const actions = [
@@ -56,7 +56,7 @@ function _askTrackMeasurements(uiViewportDialogService, viewportIndex) {
     };
 
     uiViewportDialogService.show({
-      viewportIndex,
+      viewportId,
       id: 'measurement-tracking-prompt-begin-tracking',
       type: 'info',
       message,