Improve error messages from compareArray

[ptomato]

The assert.compareArray function produces error messages like this:

Actual [up, up, down, down, left, right, left, b, a, start] and expected [up, up, down, down, left, right, left, right, b, a, start] should have the same contents.

Difficult to spot the difference at a glance. When debugging tests with long lists I've resorted to hacks like:

• Paste the error message into a text editor, turn off word wrapping, and align the opening square brackets of the actual and expected arrays on consecutive lines so I can visually see where the two arrays diverge, e.g.

  [up, up, down, down, left, right, left, b, a, start]
  [up, up, down, down, left, right, left, right, b, a, start]
  

• If running tests using Node.js as a host, patching assert.deepStrictEqual into the harness file, which produces a much more debuggable error message:

  Expected values to be strictly deep-equal:
  + actual - expected
  ... Skipped lines
  
    [
      'up',
      'up',
      'down',
      'down',
  ...
      'left',
  -   'right',
      'b',
      'a',
      'start'
    ]
  

I have no specific improvement in mind, but I'm opening this issue to follow up from our discussion in the maintainers meeting.