Remove Arrow from Split View and FIx Open Next File issue

Fixes #9041 
Fixes #9035 
Fixes #9052 
@RaymondLim 

@larz0 take a look and see if there is anything you want to do about styling the selection bar.  Since there is no more arrow, the space where there is a scroll bar is empty.  If there is no scrollbar then the selection bar goes all the way to the edge.  To see this, open just one or two files in the working set then there won't be a scrollbar. Then split the view and open a bunch of files so that there is a scrollbar. 

It looks strange that in one view it goes to the edge and in the other it leaves room for the scrollbar.