a11y: Use human name for desktop windows

When using Ctrl+Alt+TAB to switch between desktop elements, an odd name was shown in the list for the desktop icon windows. This is due to the way used to know where each window should be placed, which was encoded in the window title.

This patch changes this, setting a specific text (Desktop Icons) along with the desktop index. The extension, now, checks that specific text in the window title, and if it matches, it extracts the desktop index and gets the coordinates from inner data. This ensures that accessibility is fine.

Origin: https://gitlab.com/rastersoft/desktop-icons-ng/-/merge_requests/447
Bug-Ubuntu: https://bugs.launchpad.net/ubuntu/+source/gnome-shell-extension-desktop-icons-ng/+bug/2117725

Fix: #2117725