Sketch in a table for the keybindings UI (#32436)

Adds the initial semblance of a keymap UI. It is currently gated behind the `settings-ui` feature flag. Follow up PRs will add polish and missing features.

Release Notes:

- N/A

---------

Co-authored-by: Ben Kunkle <ben@zed.dev>
Co-authored-by: Anthony <anthony@zed.dev>

assets/keymaps/default-linux.json

@@ -1067,5 +1067,12 @@
       "ctrl-tab": "pane::ActivateNextItem",
       "ctrl-shift-tab": "pane::ActivatePreviousItem"
     }
+  },
+  {
+    "context": "KeymapEditor",
+    "use_key_equivalents": true,
+    "bindings": {
+      "ctrl-f": "search::FocusSearch"
+    }
   }
 ]

assets/keymaps/default-macos.json

@@ -1167,5 +1167,12 @@
       "ctrl-tab": "pane::ActivateNextItem",
       "ctrl-shift-tab": "pane::ActivatePreviousItem"
     }
+  },
+  {
+    "context": "KeymapEditor",
+    "use_key_equivalents": true,
+    "bindings": {
+      "cmd-f": "search::FocusSearch"
+    }
   }
 ]