fix: Update config diff check method to handle nested arrays

[camdecoster]

Description

Update config diff check to handle nested arrays.

Closes #7572.

Changes

• Linting/formatting
• Update config diff check method to handle nested arrays
• Move method to helpers file
• Add tests for method

Testing

• Be on master
• Run this mock in plotly.js DevTools:

  {
    "data": [
      {
      "error_x": {
        "array": [100000.0, 100000.0, 100000.0],
        "type": "data",
        "visible": true
      },
      "type": "scatter",
      "x": [1554370371547.085, 1554370471547.085, 1554370571547.085],
      "y": [6, 10, 2]
      }
    ],
    "layout": {
      "xaxis": {
      "type": "date"
      }
    },
    "config": {
      "modeBarButtons": [[]]
    }
  }

• Be aware that entering the next command will cause an infinite recursive loop, so add a debugger statement in react before you do to avoid crashing your browser/computer
• Call react from the browser DevTools console with the following command:

  Plotly.react(gd, gd.data, gd.layout, { modeBarButtons: [ [] ] })
  

• Click the debugger continue button a number of times and note that it just keeps happening
• Switch to this branch
• Run through the same process again
• Click the debugger continue button and note that it only runs through once

Notes

• The current diff method doesn't handle nested arrays properly, so the diff check will always return true in this case
• It didn't cause a problem before because the old code ran through react once and that was it. The new code can make a call to react recursively, which is triggered by the above example.
• It only happens with the modeBarButtons config option because that's the only one that takes a nested array as a value

TODO

• Add draftlog