project_panel: Add auto_open settings (#40435)

- Based on #40234, and improvement of #40331

Release Notes:

- Added granular settings to control when files auto-open in the project
panel (project_panel.auto_open.on_create, on_paste, on_drop)

<img width="662" height="367" alt="Screenshot_2025-10-16_17-28-31"
src="https://github.com/user-attachments/assets/930a0a50-fc89-4c5d-8d05-b1fa2279de8b"
/>

---------

Co-authored-by: Smit Barmase <heysmitbarmase@gmail.com>

assets/settings/default.json

@@ -748,8 +748,15 @@
     "hide_root": false,
     // Whether to hide the hidden entries in the project panel.
     "hide_hidden": false,
-    // Whether to automatically open files when pasting them in the project panel.
-    "open_file_on_paste": true
+    // Settings for automatically opening files.
+    "auto_open": {
+      // Whether to automatically open newly created files in the editor.
+      "on_create": true,
+      // Whether to automatically open files after pasting or duplicating them.
+      "on_paste": true,
+      // Whether to automatically open files dropped from external sources.
+      "on_drop": true
+    }
   },
   "outline_panel": {
     // Whether to show the outline panel button in the status bar