Improve workspace bindings (#33765)

* Add a "close item"-like binding to close the active dock, if present

Now, cmd/ctrl-w can be used close the focused dock before the Zed window

* Add defaults to MoveItem* actions to make it appear in the command
palette

Release Notes:

- N/A

assets/keymaps/default-linux.json

@@ -605,7 +605,9 @@
       // "foo-bar": ["task::Spawn", { "task_name": "MyTask", "reveal_target": "dock" }]
       // or by tag:
       // "foo-bar": ["task::Spawn", { "task_tag": "MyTag" }],
-      "f5": "debugger::Rerun"
+      "f5": "debugger::Rerun",
+      "ctrl-f4": "workspace::CloseActiveDock",
+      "ctrl-w": "workspace::CloseActiveDock"
     }
   },
   {

assets/keymaps/default-macos.json

@@ -659,7 +659,8 @@
       "cmd-k shift-up": "workspace::SwapPaneUp",
       "cmd-k shift-down": "workspace::SwapPaneDown",
       "cmd-shift-x": "zed::Extensions",
-      "f5": "debugger::Rerun"
+      "f5": "debugger::Rerun",
+      "cmd-w": "workspace::CloseActiveDock"
     }
   },
   {