51792 Roll engine 96061d62281d..5e474ee860a3 (29 commits) (cla: yes, waiting for tree to go green)

51801 [flutter_tools] disable mirrors in snapshot (cla: yes, waiting for tree to go green)

51808 [flutter_tools] supports tree-shake-icons for web builds (cla: yes, tool, work in progress; do not review)

51821 Roll engine 5e474ee860a3..6991dd981bf7 (10 commits) (cla: yes, waiting for tree to go green)

51832 Add pre-stable support for create on Linux (cla: yes, tool)

51838 Exit for missing Windows plugin projects (cla: yes, tool)