[flutter_tools] enable single widget reload optimization by default on master (#66507)
[flutter_tools] enable single widget reload optimization by default on master (#66507)

This should be a mostly non breaking change for hot reload workflows that improves performance, but if you see anything odd with hot reload behavior on master please file a bug. This feature can also be disabled without any changes to the SDK with flutter config --no-single-widget-reload-optimization 
cbracken/flutter,cbracken/flutter,flutter/flutter,Hixie/flutter,cbracken/flutter,flutter/flutter,Hixie/flutter,Hixie/flutter,cbracken/flutter,tvolkert/flutter,tvolkert/flutter,flutter/flutter,tvolkert/flutter,tvolkert/flutter,Hixie/flutter,cbracken/flutter,tvolkert/flutter,flutter/flutter,cbracken/flutter,cbracken/flutter,flutter/flutter,tvolkert/flutter,cbracken/flutter,tvolkert/flutter,Hixie/flutter,flutter/flutter,Hixie/flutter,flutter/flutter,flutter/flutter,flutter/flutter,cbracken/flutter,Hixie/flutter,tvolkert/flutter,Hixie/flutter,tvolkert/flutter,flutter/flutter,cbracken/flutter,Hixie/flutter,Hixie/flutter,tvolkert/flutter