List architecture in state platforms.

[mitchell-as]

DX-3216 `state platforms` shows the architecture of the platform

We will be supporting ARM soon, so we need to be able to distinguish between Linux x86 and Linux ARM.

Sample:

% state platforms
█ Listing Platforms (Beta)

Beta Feature: This feature is still in beta and may be unstable.

  Name     Version    Arch    Bit Width  
─────────────────────────────────────────
  Linux    4.18.0     arm     64         
  Linux    5.14.0     x86     64