21882 Revert “Add flag to not publish the observatory port over mDNS” (cla: yes, platform-ios)

21883 Add flag to not publish the observatory port over mDNS (cla: yes, platform-ios)

21884 Roll buildroot to 9184ff0695be1b3e4bb20cf64efcfa56daa0a3c0 (cla: yes)

21889 Fix incldues to be flutter/shell rather than shell/ (cla: yes, platform-android)

21890 Refactored the FlutterEngine to make it easier to implement spawn functionality (cla: yes, platform-ios)

21891 Check for null images in ImageFromCompressedData (cla: yes, waiting for tree to go green)