80324 Pull XCDevice out of xcode.dart (team, tool, cla: yes, waiting for tree to go green, a: null-safety)

80333 Add –dart-define to build bundle (tool, cla: yes, waiting for tree to go green)

80382 [flutter_tools] fix null check in crash reporter (tool, cla: yes)

80389 [flutter_tools] connect devtools deeplink URLs for web target platform / debug mode (tool, cla: yes)

80392 Migrate flutter_manifest to null safety (team, tool, cla: yes, waiting for tree to go green, a: null-safety)

80399 Split out XcodeProjectInterpreter from xcode_build_settings (team, tool, cla: yes, waiting for tree to go green, a: null-safety)