78975 [gen-l10n] Remove more ignores, conditionally generate some code (a: internationalization, cla: yes, tool, waiting for tree to go green)

78988 [flutter_tools] migrate tool_backend.dart to null safety and add testing of exit conditions (cla: yes, tool, waiting for tree to go green)

78995 [flutter_tools] use existing service implementations for web (cla: yes, tool, waiting for tree to go green)

79010 Removed unnecessary ! in net.dart (cla: yes, tool)

79016 Split globals.dart into null safe and unsafe libraries (a: null-safety, cla: yes, team, tool)

79047 [flutter_tools] Remove reference to Fuchsia pm genkey and -k (cla: yes, tool)