3545 Honor, and scrub, the 1.0 compatibility promise (cla: yes, p: android_intent, p: connectivity, p: device_info, p: package_info, p: path_provider, p: sensors, p: share, p: shared_preferences, p: url_launcher, p: video_player, platform-linux, platform-macos, platform-web, platform-windows)

3589 [sensors] Update to NNBD stable (cla: yes, nnbd, p: sensors)

3665 [various] Import flutter_test for future compatibility (cla: yes, p: camera, p: in_app_purchase, p: sensors, waiting for tree to go green)