28045 Fix some warnings seen after the migration to JDK 11 (platform-android, cla: yes, waiting for tree to go green, needs tests)

28056 [web] add CanvasKit to CIPD; make it a DEPS dependency; add a manual roller script (cla: yes, platform-web, needs tests)

28059 Fix memory leak in FlutterDarwinExternalTextureMetal (cla: yes, waiting for tree to go green, needs tests)

28064 [UWP] Implement clipboard. (cla: yes, waiting for tree to go green, platform-windows, needs tests)

28065 Fix memory leak in FlutterSwitchSemanticsObject (platform-ios, cla: yes, waiting for tree to go green, needs tests)

28098 [UWP] Implement setting cursor icon. (cla: yes, waiting for tree to go green, platform-windows, needs tests)