Change `restore-files` back to use "Revert" #3665

We should restore the previous wording here. "Restore file" doesn't really mean anything in this context. The git command we based this choice on required a reference to restore to.

Here there's no reference. "Undo changes" or more appropriately "Revert changes" would be easier to understand.

Also since now we have highlight-deleted-and-added-files-in-diffs, we can use this piece of information, if found, to customize it:

• changed file: "Revert changes"
• deleted file: "Restore file"
• added file: nothing, there's already a "Delete file"

This logic would be in addition to the current one. If the icons are not found/ready, then the menuitem should use the default "Revert changes"