Keyboard Test: More realistic layout

As you can see here, I've manually entered all the keycodes for a V2 US keyboard:

But the layout isn't like the real keyboard, which can be confusing for the operator.

Please make it so that one can define (horizontal) rows in the keys_config.json that contain a group of keys each, and display them accordingly in the keyboard testing window.

Here is a picture of the actual layout of a V2 US keyboard: https://i.redd.it/1j5pr59q99881.jpg

And a V3: https://shop.mntre.com/spree/products/374/large/2023-05-refkbd-v3-front-black.jpg?1684759383