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 

Submitted https://github.com/adobe/brackets/pull/8117 .

I think `expectInMemory()` just needs to verify that working set size is same as file array size.