Add Replace in... to context menus

Add "Replace in..." to project tree and working set context menus.

https://trello.com/c/3cKG28Fn/1309-replace-in-from-file-tree

cc @njx 

BTW, I think the reason it passes is that `expectInMemoryFiles()` will check that the given file is open and has the right content, but it won't check that no other files got opened from the search. You'd need to check that explicitly.