Drupal 11 compatibility fixes for panelizer [v4]

Hi,

I have fixed the Panelizer for Drupal 11 compatibility and created a patch, as attached, for your reference. Please review it at your earliest convenience. Thank you.

Need to fix the failing test.

I'm inclined to say "no" on this - we need to completely drop support for Panelizer and sites need to move away from it to use core's Layout Builder.

@damienmckenna → Thank you for your insights. I’ll mark this issue as closed (won't fix).