open picker (#14524)

Release Notes:

- linux: Added a fallback Open picker for when XDG is not working
- Added a new setting `use_system_path_prompts` (default true) that can
be disabled to use Zed's builtin keyboard-driven prompts.

---------

Co-authored-by: Max <max@zed.dev>

assets/settings/default.json

@@ -94,6 +94,9 @@
   //  3. Never close the window
   //         "when_closing_with_no_tabs": "keep_window_open",
   "when_closing_with_no_tabs": "platform_default",
+  // Whether to use the system provided dialogs for Open and Save As.
+  // When set to false, Zed will use the built-in keyboard-first pickers.
+  "use_system_path_prompts": true,
   // Whether the cursor blinks in the editor.
   "cursor_blink": true,
   // How to highlight the current line in the editor.