Ensure pane: swap item right does not panic (#36765)

This fixes a panic I randomly ran into whilst mistyping in the command
palette: I accidentally ran `pane: swap item right`in a state where no
items were opened in my active pane. We were checking for `index + 1 ==
self.items.len()` there when it really should be `>=`, as otherwise in
the case of no items this panics.

This PR fixes the bug, adds a test for both the panic as well as the
actions themselves (they were untested previously). Lastly (and mostly),
this also cleans up a bit around existing actions to update them with
how we generally handle actions now.

Release Notes:

- Fixed a panic that could occur with the `pane: swap item right`
action.

crates/editor/src/editor_tests.rs

@@ -22715,7 +22715,7 @@ async fn test_invisible_worktree_servers(cx: &mut TestAppContext) {
     .await
     .unwrap();
     pane.update_in(cx, |pane, window, cx| {
-        pane.navigate_backward(window, cx);
+        pane.navigate_backward(&Default::default(), window, cx);
     });
     cx.run_until_parked();
     pane.update(cx, |pane, cx| {
@@ -24302,7 +24302,7 @@ async fn test_document_colors(cx: &mut TestAppContext) {
     workspace
         .update(cx, |workspace, window, cx| {
             workspace.active_pane().update(cx, |pane, cx| {
-                pane.navigate_backward(window, cx);
+                pane.navigate_backward(&Default::default(), window, cx);
             })
         })
         .unwrap();