pane: 'Close others' now closes relative to right-clicked tab (#34355)

Closes #33445

Fixed the "Close others" context menu action to close tabs relative to
the right-clicked tab instead of the currently active tab. Previously,
when right-clicking on an inactive tab and selecting "Close others", it
would keep the active tab open rather than the right-clicked tab.

## Before/After

https://github.com/user-attachments/assets/d76854c3-c490-4a41-8166-309dec26ba8a



## Changes

- Modified `close_inactive_items()` method to accept an optional
`target_item_id` parameter
- Updated context menu handler to pass the right-clicked tab's ID as the
target
- Maintained backward compatibility by defaulting to active tab when no
target is specified
- Updated all existing call sites to pass `None` for the new parameter

Release Notes:

- Fixed: "Close others" context menu action now correctly keeps the
right-clicked tab open instead of the active tab

crates/collab/src/tests/following_tests.rs

@@ -1013,7 +1013,7 @@ async fn test_peers_following_each_other(cx_a: &mut TestAppContext, cx_b: &mut T
     // and some of which were originally opened by client B.
     workspace_b.update_in(cx_b, |workspace, window, cx| {
         workspace.active_pane().update(cx, |pane, cx| {
-            pane.close_inactive_items(&Default::default(), window, cx)
+            pane.close_inactive_items(&Default::default(), None, window, cx)
                 .detach();
         });
     });