71664 Updated Interactive Scrollbars (a: desktop, cla: yes, f: cupertino, f: material design, f: scrolling, framework, platform-web, severe: new feature, waiting for tree to go green)

71707 Add stretch property to CupertinoSliverNavigationBar (cla: yes, f: cupertino, framework)

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)

71853 Add previews for CupertinoIcons (cla: yes, f: cupertino, f: material design, framework, team, waiting for tree to go green)