fix(cdk/scrolling): prevent subpixel gaps in virtual scroll viewport (#31940)

Co-authored-by: MR-KRAMA <[email protected]>
(cherry picked from commit 2918e28)

Author: Mr-KRAMA

src/cdk/scrolling/fixed-size-virtual-scroll.ts

@@ -174,7 +174,7 @@ export class FixedSizeVirtualScrollStrategy implements VirtualScrollStrategy {
     }
 
     this._viewport.setRenderedRange(newRange);
-    this._viewport.setRenderedContentOffset(this._itemSize * newRange.start);
+    this._viewport.setRenderedContentOffset(Math.round(this._itemSize * newRange.start));
     this._scrolledIndexChange.next(Math.floor(firstVisibleIndex));
   }
 }