R1:37a03402bc44

When following a link to a particular line ("/example.txt$12"), scroll to that line

Summary:
Depends on D19349. Ref T13105. This was the behavior in Diffusion before with a little hard-coded snippet.

Remove that snippet ("diffusion-jump-to") and add a more general-purpose snippet to SourceView.

This is a tiny bit hacky still (and probably doesn't work quite right with Quicksand) but gets things working again and works in all of Files, Paste, and Diffusion.

Test Plan: Followed links to particular lines…