NumberSpinner: add arrowButtonOptions, nested options for arrowButtons

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From phetsims/natural-selection#192 (comment):

I discovered that NumberSpinner has no way to dilate the pointer areas for its arrow buttons. Doing that properly involves adding nested options arrowButtonOptions to NumberSpinner, and fixing up every place where NumberSpinner is used. It will take at least 2 hours. @ariel-phet Do you want me to tackle that?

There are 12 occurrences of "import NumberSpinner" in the PhET code base.

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This section of code in NumberSpinner.js shows the options that need to be nested:

    // buttons
    const arrowButtonOptions = {
      baseColor: options.arrowButtonFill,
      stroke: options.arrowButtonStroke,
      lineWidth: options.arrowButtonLineWidth,
      focusable: false,

      // as requested in https://github.com/phetsims/sun/issues/575
      enabledPropertyOptions: {
        phetioReadOnly: true,
        phetioFeatured: false
      }
    };

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Nevermind. I found these options that work for Natural Selection:

      // arrow button pointer areas
      touchAreaXDilation: 0,
      touchAreaYDilation: 0,
      mouseAreaXDilation: 0,
      mouseAreaYDilation: 0,

Closing.