25998 Sped up the objc standard message codec (platform-ios, cla: yes, platform-macos)

25999 Roll Dart SDK from b8f4018535fa to 86c749398b3a (16 revisions) (cla: yes, waiting for tree to go green)

26001 Roll Fuchsia Mac SDK from uQgs5ZmFq… to aCsEHpnS0… (cla: yes, waiting for tree to go green)

26003 Add dependency on Windows SDK CIPD package (cla: yes)

26006 Roll Dart SDK from 86c749398b3a to b4210cc43086 (2 revisions) (cla: yes, waiting for tree to go green)