67057 update stack_trace dep (and others) (cla: yes, team, tool, waiting for tree to go green)

67081 [web] Update index.html template to support new path strategy (cla: yes, f: routes, platform-web, tool, waiting for tree to go green)

67088 [web] Respond with 404 to non-found asset or package files (cla: yes, platform-web, tool, waiting for tree to go green)

67106 [null-safety] allow web shard to compile null-safe tests. (a: null-safety, cla: yes, tool)

67146 [flutter_tools] remove globals from desktop configuration (cla: yes, tool, waiting for tree to go green)

67150 [flutter_tools] support all engine debugging options with FLUTTER_ENGINE_SWITCH environment variables (cla: yes, tool)