Add check-11-bigsur-compatibility script

[oliverweinm]

This PR adds a script that checks the current machine's compatibility with macOS Big Sur. It has been modelled on and refactors code from the previous check-xx-compatibility scripts.

The supported models and board IDs were taken from the macOS 11.3 (Build 20E232) install package. The script has been tested on several Intel Macs, but no M1 Macs yet. Testing this script on an M1 Mac, if available, would be gladly appreciated.