keymap_ui: Dim keybinds that are overridden by other keybinds (#34952)

This change dims rows in the keymap editor for which the corresponding
keybind is overridden by other keybinds coming from higher priority
sources.

Release Notes:

- N/A

assets/keymaps/default-linux.json

@@ -1137,7 +1137,10 @@
       "alt-ctrl-f": "keymap_editor::ToggleKeystrokeSearch",
       "alt-c": "keymap_editor::ToggleConflictFilter",
       "enter": "keymap_editor::EditBinding",
-      "alt-enter": "keymap_editor::CreateBinding"
+      "alt-enter": "keymap_editor::CreateBinding",
+      "ctrl-c": "keymap_editor::CopyAction",
+      "ctrl-shift-c": "keymap_editor::CopyContext",
+      "ctrl-t": "keymap_editor::ShowMatchingKeybinds"
     }
   },
   {

assets/keymaps/default-macos.json

@@ -1239,7 +1239,10 @@
       "cmd-alt-f": "keymap_editor::ToggleKeystrokeSearch",
       "cmd-alt-c": "keymap_editor::ToggleConflictFilter",
       "enter": "keymap_editor::EditBinding",
-      "alt-enter": "keymap_editor::CreateBinding"
+      "alt-enter": "keymap_editor::CreateBinding",
+      "cmd-c": "keymap_editor::CopyAction",
+      "cmd-shift-c": "keymap_editor::CopyContext",
+      "cmd-t": "keymap_editor::ShowMatchingKeybinds"
     }
   },
   {