51916 Fix simctl process exceptions not being caught (cla: yes, tool, waiting for tree to go green)

51920 Remove target platform override on the gallery. (cla: yes, d: examples, team, team: gallery)

51921 Add an adaptive visual density static function, and add it to the sample app. (cla: yes, f: material design, framework)

51925 Custom onPressed behavior for CloseButton widget (cla: yes, f: material design, framework, waiting for tree to go green)

51938 Roll engine 90bd6f814817..e2b74ab80eb4 (4 commits) (cla: yes, waiting for tree to go green)

51943 Revert “Write FLUTTER_BUILD_MODE when using a local engine” (cla: yes, tool)