test(e2e): replace waitForVolumeLoad with viewport render waits (#6000)

tests/MPRThenRTOverlayNoHydration.spec.ts

@@ -1,4 +1,11 @@
-import { checkForScreenshot, screenShotPaths, test, visitStudy } from './utils';
+import {
+  checkForScreenshot,
+  screenShotPaths,
+  test,
+  visitStudy,
+  waitForViewportRenderCycle,
+  waitForViewportsRendered,
+} from './utils';
 import { assertNumberOfModalityLoadBadges } from './utils/assertions';
 
 test.beforeEach(async ({ page }) => {
@@ -14,7 +21,7 @@ test('should launch MPR with unhydrated RTSTRUCT chosen from the data overlay me
 }) => {
   await mainToolbarPageObject.layoutSelection.MPR.click();
 
-  await mainToolbarPageObject.waitForVolumeLoad();
+  await waitForViewportsRendered(page);
 
   await checkForScreenshot(
     page,
@@ -27,6 +34,8 @@ test('should launch MPR with unhydrated RTSTRUCT chosen from the data overlay me
   await sagittalViewport.pane.hover();
   const dataOverlayPageObject = sagittalViewport.overlayMenu.dataOverlay;
   await dataOverlayPageObject.toggle();
+
+  const viewportRenderCycle = waitForViewportRenderCycle(page);
   await dataOverlayPageObject.addSegmentation('ARIA RadOnc Structure Sets');
 
   // Hide the overlay menu.
@@ -35,7 +44,7 @@ test('should launch MPR with unhydrated RTSTRUCT chosen from the data overlay me
   // Adding an overlay should not show the LOAD button.
   await assertNumberOfModalityLoadBadges({ page, expectedCount: 0 });
 
-  await mainToolbarPageObject.waitForVolumeLoad();
+  await viewportRenderCycle;
 
   await checkForScreenshot({
     page,