Default to Mac keyboard layout on Mac hardware

Tails on a Mac defaults to a PC keyboard configuration. It is presumably not hard to detect the hardware is made by Apple and make a Mac keyboard layout the default one:

the default layout in the Greeter should English for Mac
when I type “fr” to have French keyboard, the Greeter filters all non-French layouts, and then when I type ENTER the French layout for Mac should be selected; similarly, if I don’t use the keyboard but click “Dutch”, I sholud get the Dutch for Mac layout

Related issues

Related to #7779 (closed)
Related to #14544
Related to #5501

Original created by @tails on 5722 (Redmine)

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information