[Bug] When using matrix to draw a 'heatmap', series.encode does not seem to work for setting the 'value'

### Version

6.0.0

### Link to Minimal Reproduction

https://echarts.apache.org/examples/en/editor.html

### Steps to Reproduce

Copy paste the code into the Echarts graph library:

```
// Dataset with multiple value columns
// Expected: use 'value1' (0.1, 0.2, 0.3, 0.4)
// Actual: uses 'value3' (last column: 0.9, 0.8, 0.7, 0.6)
var dataset = {
source: [
['x', 'y', 'value1', 'value2', 'value3'],
['A', 'X', 0.1, 0.5, 0.9],
['A', 'Y', 0.2, 0.6, 0.8],
['B', 'X', 0.3, 0.7, 0.7],
['B', 'Y', 0.4, 0.8, 0.6]
]
};

var xData = [
{ value: 'Group1', children: [{ value: 'A' }, { value: 'B' }] }
];

var yData = [
{ value: 'Group1', children: [{ value: 'X' }, { value: 'Y' }] }
];

var option = {
dataset: dataset,
matrix: {
top: 80,
bottom: 80,
left: 120,
right: 30,
x: {
data: xData,
levels: [{ levelSize: 20 }, { levelSize: 50 }]
},
y: {
data: yData,
levels: [{ levelSize: 20 }, { levelSize: 50 }]
}
},
series: [{
type: 'heatmap',
coordinateSystem: 'matrix',
encode: {
x: 'x',
y: 'y',
value: 'value1' // <-- BUG: This is ignored, uses 'value3' instead
},
datasetIndex: 0
}],
visualMap: {
type: 'continuous',
min: 0,
max: 1,
calculable: true,
orient: 'vertical',
left: 10,
top: 80,
inRange: {
color: ['#ffffff', '#006400']
}
},
tooltip: {
show: true,
formatter: function (params) {
var d = params.data;
return `x: ${d[0]}
y: ${d[1]}
` +
`value1 (expected): ${d[2]}
` +
`value2: ${d[3]}
` +
`value3 (actual used): ${d[4]}`;
}
}
};
```

### Current Behavior

It seems that the `x` and `y` in the encode seems to work, but the `value` is ignored, it takes the last column in the dataset for it.

```
... example ...
source: [
['x', 'y', 'value1', 'value2', 'value3'],
['A', 'X', 0.1, 0.5, 0.9],
['A', 'Y', 0.2, 0.6, 0.8],
['B', 'X', 0.3, 0.7, 0.7],
['B', 'Y', 0.4, 0.8, 0.6]
]
... example ...
encode: {
x: 'x',
y: 'y',
value: 'value1' // <-- BUG: This is ignored, uses 'value3' instead
}
... example ...
```

### Expected Behavior

The `value1` should be used to display the color shading and not the `value3`, when the encode is `value: 'value1`

### Environment

```markdown
- OS: Windows 11
- Browser: Microsoft edge
- Framework: Echarts website framework
```

### Any additional comments?

_No response_