feat: add channels to style and label callback

[pearmini]

fix: #6248

对于聚合图表，需要提供聚合之后的数据给 label 和 style 的回调，这样才能根据聚合后的数据进行可视化。

export function diamondIntervalGroupX(): G2Spec {
  return {
    type: 'interval',
    data: {
      type: 'fetch',
      value: 'data/diamond.csv',
    },
    encode: {
      x: 'clarity',
      y: 'price',
    },
    labels: [
      {
        text: (_, index, __, {channel}) => channel.y[index],
      },
    ],
    transform: [{ type: 'groupX', y: 'max' }],
    style: {
      fill: (_, index, __, {channel}) =>
        channel.y[index] < 11700 ? 'red' : 'blue',
    },
  };
}

[coveralls]

Pull Request Test Coverage Report for Build 9283375010

Details

• 7 of 7 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.002%) to 86.409%

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Totals
Change from base Build 9243141786:	0.002%
Covered Lines:	10374
Relevant Lines:	11629

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💛 - Coveralls