如何在 Vue3 + Element Plus 中实现复杂的 el-table 表格功能，如横、列动态渲染，含有二级分类，并支持合并行和列？

<el-table :span-method="arrayspanmethod" :data="tabledata">
  <el-table-column label="派出组" align="center" prop="group"></el-table-column>
  <el-table-column label="累计生产单" align="center" prop="total"></el-table-column>
  <el-table-column label="案件主办" align="center" prop="person"></el-table-column>
  <el-table-column
    v-for="(item, index) in headerlist"
    :key="index"
    :label="item.label"
    align="center"
    :prop="item.prop"
  >
    <el-table-column
      v-for="(list, i) in item.sublist"
      :key="i"
      :label="list.label"
      align="center"
      :prop="list.prop"
    >
      <template #default="scope">{{ scope.row[item.prop][list.prop] }}</template>
    </el-table-column>
  </el-table-column>
</el-table>

// 模拟后台返回的表格头部信息
const headerList = [
  {
    label: '达飞',
    prop: 'column1',
    subList: [
      {
        label: '保理当日',
        prop: 'day'
      },
      {
        label: '保理累计',
        prop: 'total'
      }
    ]
  },
  {
    label: '农行',
    prop: 'column2',
    subList: [
      {
        label: '农行秦分当日',
        prop: 'day'
      },
      {
        label: '农行秦分累计',
        prop: 'total'
      }
    ]
  }
];

// 模拟后台返回的表格数据信息
const tableData = [
  {
    group: '海港组',
    total: 123,
    person: 'aa',
    column1: {
      day: '500',
      total: 3000
    },
    column2: { day: 100, total: 3000 }
  },
  {
    group: '海港组',
    total: 123,
    person: 'bb',
    column1: {
      day: '500',
      total: 3000
    },
    column2: { day: 100, total: 3000 }
  },
  {
    group: '海港组',
    total: 123,
    person: 'cc',
    column1: {
      day: '500',
      total: 3000
    },
    column2: { day: 100, total: 3000 }
  },
  {
    group: '其他组',
    total: 123,
    person: 'cc',
    column1: {
      day: '500',
      total: 3000
    },
    column2: { day: 100, total: 3000 }
  },
  {
    group: '其他组',
    total: 123,
    person: 'cc',
    column1: {
      day: '500',
      total: 3000
    },
    column2: { day: 100, total: 3000 }
  },
  {
    group: '其他组',
    total: 234,
    person: 'cc',
    column1: {
      day: '500',
      total: 3000
    },
    column2: { day: 100, total: 3000 }
  }
];

// 用于合并组
const groupArr = [];

// 用于合并生产单
const totalArr = [];

// 表格行合并方法
const merge = (tableData) => {
  for (var i = 0; i < tableData.length; i++) {
    if (i === 0) {
      // 第一行必须存在
      groupArr.push(1);
      totalArr.push(1);
    } else {
      // 判断当前元素与上一个元素是否相同
      if (tableData[i].group === tableData[i - 1].group) {
        groupArr[groupArr.length - 1] += 1;
      } else {
        groupArr.push(1);
      }

      // 生产单合并
      if (
        tableData[i].total === tableData[i - 1].total &&
        tableData[i].group === tableData[i - 1].group
      ) {
        totalArr[totalArr.length - 1] += 1;
      } else {
        totalArr.push(1);
      }
    }
  }
};

// 合并行
const arraySpanMethod = ({ row, column, rowIndex, columnIndex }) => {
  if (columnIndex === 0) {
    // 合并组
    const _row_1 = groupArr[rowIndex];
    const _col_1 = _row_1 > 0 ? 1 : 0;
    return {
      rowspan: _row_1,
      colspan: _col_1
    };
  } else if (columnIndex === 1) {
    // 合并生产单
    const _row_2 = totalArr[rowIndex];
    const _col_2 = _row_2 > 0 ? 1 : 0;
    return {
      rowspan: _row_2,
      colspan: _col_2
    };
  }
};

merge(tableData.value);