Merge Workspace::save_item into Pane::save_item

These methods were slightly different which caused (for example) there
to be no "Discard" option in the conflict case at the workspace level.

To make this work, a new SaveBehavior (::PromptForNewPath) was added to
support SaveAs.
88a32ae48dConrad Irwin committed on 9/21/2023, 2:44:26 AMparenta4f96e6
2 files changedLine totals unavailable