fix(position): auto position append to body
fix(position): auto position append to body

- Use the body as the viewport to determine available size for
auto position when the target element is append-to-body

Closes #5582
Fixes #5576

looker/bootstrap,Kpler/bootstrap,vfiles/bootstrap,Servoy/bootstrap,christor/bootstrap,mabi/bootstrap,icfantv/bootstrap,fpipita/bootstrap,BookingBug/bootstrap,RobJacobs/bootstrap,caoruiy/bootstrap,benhalverson/bootstrap,angular-ui/bootstrap,caoruiy/bootstrap,christor/bootstrap,Foxandxss/bootstrap,byronigoe/bootstrap,292388900/bootstrap,benhalverson/bootstrap,shootermv/bootstrap,byronigoe/bootstrap,Servoy/bootstrap,vfiles/bootstrap,icfantv/bootstrap,angular-ui/bootstrap,wesleycho/bootstrap,benhalverson/bootstrap,looker/bootstrap,Foxandxss/bootstrap,benhalverson/bootstrap,BookingBug/bootstrap,fpipita/bootstrap,Kpler/bootstrap,RobJacobs/bootstrap,shootermv/bootstrap,mabi/bootstrap,wesleycho/bootstrap,292388900/bootstrap