Refactor Effen to make explicit the distinction between render & non-render nodes.
Refactor Effen to make explicit the distinction between render & non-render nodes.

All Effen which can directly create a sky.Node are now derived from RenderNode. In contrast, Component now derives from the (now) base Node class which simply represents a position in the Effen hierarchy.

A fair amount of clean-up & refactoring went into this change, simplifying & unifying the "sync" logic between Element & Component as well as making the Component.didMount/didUnmount signals async WRT component building.

BUG=
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1009543008

jason-simmons/sky_engine,jamesr/sky_engine,krisgiesing/sky_engine,TribeMedia/sky_engine,TribeMedia/sky_engine,jason-simmons/flutter_engine,mpcomplete/flutter_engine,abarth/sky_engine,takaaptech/sky_engine,TribeMedia/sky_engine,takaaptech/sky_engine,mxia/engine,xunmengfeng/engine,krisgiesing/sky_engine,chinmaygarde/flutter_engine,chinmaygarde/sky_engine,jamesr/flutter_engine,mpcomplete/engine,chinmaygarde/sky_engine,cdotstout/sky_engine,jamesr/flutter_engine,qiankunshe/sky_engine,xunmengfeng/engine,mdakin/engine,iansf/sky_engine,jamesr/flutter_engine,afandria/sky_engine,afandria/sky_engine,qiankunshe/sky_engine,xunmengfeng/engine,jamesr/flutter_engine,krisgiesing/sky_engine,axinging/sky_engine,jamesr/sky_engine,Hixie/sky_engine,qiankunshe/sky_engine,mikejurka/engine,chinmaygarde/flutter_engine,mdakin/engine,cdotstout/sky_engine,qiankunshe/sky_engine,jamesr/flutter_engine,flutter/engine,jason-simmons/flutter_engine,afandria/sky_engine,afandria/sky_engine,axinging/sky_engine,mpcomplete/flutter_engine,krisgiesing/sky_engine,chinmaygarde/flutter_engine,tvolkert/engine,Hixie/sky_engine,rmacnak-google/engine,afandria/sky_engine,jimsimon/sky_engine,jason-simmons/sky_engine,TribeMedia/sky_engine,chinmaygarde/flutter_engine,xunmengfeng/engine,jason-simmons/sky_engine,takaaptech/sky_engine,TribeMedia/sky_engine,flutter/engine,axinging/sky_engine,cdotstout/sky_engine,mikejurka/engine,zhangxq5012/sky_engine,mxia/engine,jason-simmons/flutter_engine,jason-simmons/sky_engine,abarth/sky_engine,devoncarew/engine,devoncarew/engine,jason-simmons/sky_engine,jason-simmons/flutter_engine,mpcomplete/engine,takaaptech/sky_engine,aam/engine,mpcomplete/engine,iansf/sky_engine,flutter/engine,jamesr/sky_engine,devoncarew/sky_engine,devoncarew/sky_engine,tvolkert/engine,lyceel/engine,mdakin/engine,qiankunshe/sky_engine,Hixie/sky_engine,iansf/sky_engine,chinmaygarde/sky_engine,cdotstout/sky_engine,abarth/sky_engine,Hixie/sky_engine,chinmaygarde/flutter_engine,axinging/sky_engine,axinging/sky_engine,jamesr/flutter_engine,jason-simmons/flutter_engine,mpcomplete/flutter_engine,jimsimon/sky_engine,devoncarew/engine,devoncarew/sky_engine,axinging/sky_engine,jamesr/flutter_engine,jason-simmons/flutter_engine,chinmaygarde/flutter_engine,takaaptech/sky_engine,flutter/engine,cdotstout/sky_engine,jamesr/sky_engine,rmacnak-google/engine,devoncarew/sky_engine,cdotstout/sky_engine,TribeMedia/sky_engine,jimsimon/sky_engine,aam/engine,takaaptech/sky_engine,devoncarew/engine,lyceel/engine,flutter/engine,chinmaygarde/sky_engine,aam/engine,abarth/sky_engine,chinmaygarde/sky_engine,mikejurka/engine,jason-simmons/flutter_engine,tvolkert/engine,rmacnak-google/engine,flutter/engine,mikejurka/engine,mdakin/engine,jason-simmons/flutter_engine,jimsimon/sky_engine,iansf/sky_engine,jamesr/sky_engine,chinmaygarde/flutter_engine,mikejurka/engine,mxia/engine,mxia/engine,takaaptech/sky_engine,xunmengfeng/engine,mpcomplete/flutter_engine,mdakin/engine,aam/engine,zhangxq5012/sky_engine,afandria/sky_engine,jimsimon/sky_engine,Hixie/sky_engine,lyceel/engine,mxia/engine,zhangxq5012/sky_engine,xunmengfeng/engine,lyceel/engine,lyceel/engine,rmacnak-google/engine,flutter/engine,krisgiesing/sky_engine,rmacnak-google/engine,rmacnak-google/engine,mpcomplete/flutter_engine,tvolkert/engine,axinging/sky_engine,aam/engine,iansf/sky_engine,krisgiesing/sky_engine,jamesr/flutter_engine,aam/engine,takaaptech/sky_engine,axinging/sky_engine,afandria/sky_engine,lyceel/engine,qiankunshe/sky_engine,chinmaygarde/sky_engine,devoncarew/sky_engine,aam/engine,takaaptech/sky_engine,iansf/sky_engine,mpcomplete/engine,jimsimon/sky_engine,afandria/sky_engine,aam/engine,devoncarew/engine,devoncarew/sky_engine,jimsimon/sky_engine,mxia/engine,flutter/engine,zhangxq5012/sky_engine,jamesr/flutter_engine,mdakin/engine,zhangxq5012/sky_engine,xunmengfeng/engine,jamesr/sky_engine,qiankunshe/sky_engine,abarth/sky_engine,jimsimon/sky_engine,devoncarew/sky_engine,TribeMedia/sky_engine,mikejurka/engine,cdotstout/sky_engine,abarth/sky_engine,mpcomplete/engine,mikejurka/engine,qiankunshe/sky_engine,mdakin/engine,jimsimon/sky_engine,TribeMedia/sky_engine,chinmaygarde/sky_engine,tvolkert/engine,mpcomplete/flutter_engine,krisgiesing/sky_engine,mpcomplete/engine,iansf/sky_engine,axinging/sky_engine,zhangxq5012/sky_engine,mxia/engine,Hixie/sky_engine,jason-simmons/sky_engine,lyceel/engine,mxia/engine,mikejurka/engine,rmacnak-google/engine,mdakin/engine,devoncarew/engine,tvolkert/engine,Hixie/sky_engine,zhangxq5012/sky_engine,zhangxq5012/sky_engine,TribeMedia/sky_engine,tvolkert/engine,jason-simmons/sky_engine,devoncarew/engine,mpcomplete/engine,mikejurka/engine,abarth/sky_engine,Hixie/sky_engine,mpcomplete/engine,jamesr/sky_engine,zhangxq5012/sky_engine,iansf/sky_engine