67940 Fix NestedScrollView sample code (a: quality, cla: yes, d: api docs, d: examples, documentation, framework, waiting for tree to go green)

69063 Add horizontal gesture support for CupertinoScrollbar (a: desktop, a: quality, cla: yes, f: cupertino, f: scrolling, framework, waiting for tree to go green)

69383 Fix the PopupMenuButton offset bug (a: quality, cla: yes, f: material design, framework, waiting for tree to go green)

71843 Improve the ScrollBar behavior when nested (a: quality, cla: yes, f: cupertino, f: material design, f: scrolling, framework, severe: new feature, waiting for tree to go green)