Auto show popup after Next Change or Previous Change command

[sharwell]

Update the Jump to Next Change and Jump to Previous Change implementations to automatically show the popup for the target change. This feature required changing the location where the popup appears to be relative to the actual diff instead of relative to the cursor. The behavior would be improved if it were further updated to use the custom placement only in response to the Jump to Next Change or Jump to Previous Change commands, and use the mouse placement when the diff is actually clicked in the margin.