27694 UWP: Fix uwptools that does not uninstall package (cla: yes, platform-windows, needs tests)

27749 hasStrings on Windows (cla: yes, waiting for tree to go green, platform-windows)

27757 Rename fl_get_length to fl_value_get_length (cla: yes, waiting for tree to go green, platform-linux)

27760 Do not call CoreWindow::Visible from raster thread (cla: yes, platform-windows, needs tests)

27786 fix crash SemanticsObject dealloc and access the children (platform-ios, cla: yes, waiting for tree to go green, needs tests)

27849 [fuchsia] [ffi] Basic support for Channels and Handles (cla: yes, waiting for tree to go green, platform-fuchsia)