For #11404 - Add 'Open all in private tabs' option as requested.

mozilla-mobile/fenix#21212 (comment)

- Add option is tree dot menu
- Edit folder opening to be aware of browsing mode
- Add metrics
- Add unit tests for 'Open all in private tabs'
- Add Android tests for open all in private.

X-Channel-Revision: [main] mozilla-mobile/android-components@f6e7218
X-Channel-Converted-Revision: [main] mozilla-mobile/fenix@fe16a81
X-Channel-Revision: [main] mozilla-mobile/focus-android@7ca4851

_meta/mozilla-mobile-fenix.json

@@ -1,6 +1,6 @@
 {
   "name": "mozilla-mobile/fenix",
   "revs": {
-    "main": "9cf42cb7d91e49d693ad585fd95afb6efb621d91"
+    "main": "fe16a81c1df204f42dc0389fdaffd1f8ada49b73"
   }
 }

mozilla-mobile/fenix/app/src/main/res/values/strings.xml

@@ -862,6 +862,8 @@
     <string name="bookmark_menu_open_in_private_tab_button">Open in private tab</string>
     <!-- Bookmark overflow menu open all in tabs button -->
     <string name="bookmark_menu_open_all_in_tabs_button">Open all in new tabs</string>
+    <!-- Bookmark overflow menu open all in private tabs button -->
+    <string name="bookmark_menu_open_all_in_privates_button">Open all in private tabs</string>
     <!-- Bookmark overflow menu delete button -->
     <string name="bookmark_menu_delete_button">Delete</string>
     <!--Bookmark overflow menu save button -->