Add OpenExcerptsSplit (#8574)

I would like to keep diagnostics open on one side, and process them on
the other.


Release Notes:

- Added `editor::OpenExcerptsSplit` (bound to `cmd-k enter`) to open the
selected excerpts in the adjacent pane
- vim: Added `ctrl-w d`, `ctrl-w shift-d` and `ctrl-w space` for
`editor::GoTo{,Type}Definition` and `editor::OpenExcerptsSplit`

crates/terminal_view/src/terminal_view.rs

@@ -132,7 +132,7 @@ impl TerminalView {
                     cx,
                 )
             });
-            workspace.add_item(Box::new(view), cx)
+            workspace.add_item_to_active_pane(Box::new(view), cx)
         }
     }