[Feature] Adjacent crosshairs must be close together

[da730]

What problem does this feature solve?

Adjacent crosshairs must be close together with no gaps, just like 3.x:

What does the proposed API look like?

need to be discussed

[kkxxkk2019]

1.7.3 会对 type: 'rect' 类型的 �line 上的 width 属性支持回调，回调将会返回该 crosshair 对应轴的信息，可以根据轴信息动态计算，如：

crosshair: {
  xField: {
    line: {
      type: 'rect',
      width: ({width}, axis) => {
         return (width / axis.getScale().ticks().length);
     } 
    }
  }
}