feat: open changed MR file using a context menu in the TreeView

This MR introduces a new way to access the "Open Changed File in Local Project" feature. Currently there is only a button in the editor panel, but after talking to a few people, I don't think that it is discoverable. So I added a tree view item button (thank you for the suggestion to use a button @X_Sheep 🙏 )

original button	tree view item button
open-mr-file-orig	open-mr-file-inline