apple-t2: remove ifd and cleanup drv

[Frontear]

Description of changes

This was originally going to be a PR fixing all IFDs found in nixos-hardware, but I could only find two:

1. apple-t2
2. toshiba-swanky

apple-t2 was easily fixable, and in the process the drv itself was cleaned up, but toshiba-swanky is a bit more problematic due to the use of system.replaceRuntimeDependencies, which is by nature impure and IFD.

Given the above, this PR has been adjusted to only fix up the apple-t2 IFD.

Note: Testing for the IFDs was iterative and I am very confident I did not miss any. It was done through iterative generation of nixos configurations that imported each module and set relevant setting to allow evaluation at minimum.

Things done

• Tested the changes in your own NixOS Configuration
• Tested the changes end-to-end by using your fork of nixos-hardware and
  importing it via <nixos-hardware> or Flake input

[Mic92]

toshiba swanky is a bit older now: https://chromebookdb.com/chromebook/toshiba-chromebook-2-cb35-b3340
I wonder if it is still in use?

[Frontear]

toshiba swanky is a bit older now: chromebookdb.com/chromebook/toshiba-chromebook-2-cb35-b3340 I wonder if it is still in use?

Honestly great question, it's not a bad idea to do a sweep of nixos-hardware and start deprecating really old things. A warning first, then complete removal