Closes https://github.com/zed-industries/zed/issues/19731

Adds `editor::GoToPreviousChange` and `editor::GoToNextChange` that work
the same as `vim::ChangeListOlder` and `vim::ChangeListNewer` as the
common logic was extracted and reused.

Release Notes:

- Added a way to navigate between changes with
`editor::GoToPreviousChange` and `editor::GoToNextChange`