fix: update legend component inferring strategies

[Aarebecca]

通过比例尺推断组件添加了额外的规则：

1. 如果比例尺全为常量比例尺，则不推断图例
2. 如果组件为连续图例，其颜色比例尺必须指定domain

fixed #4904

[pearmini]

如果组件为连续图例，其颜色比例尺必须指定domain

为啥需要这个限制？

[Aarebecca]

如果组件为连续图例，其颜色比例尺必须指定domain

为啥需要这个限制？

没有颜色的话或者单一颜色，绘制连续比例尺应该没有意义

[Aarebecca]

图例组件推断关系

例子：
当前比例尺组合为： color 通道为离散比例尺，shape 通道为 常数比例尺
则会匹配上第规则 27，因此可以使用分类图例

如果比例尺组合为：shape 通道为离散比例尺，size 通道为 常数比例尺
则没有可匹配的规则，因此当前比例尺组合不会推断出图例

legendCategory

1. color-discrete opacity-discrete shape-discrete size-constant
2. color-discrete opacity-constant shape-discrete size-constant
3. color-discrete opacity-discrete shape-constant size-constant
4. color-discrete opacity-constant shape-constant size-constant
5. color-constant opacity-discrete shape-discrete size-constant
6. color-constant opacity-constant shape-discrete size-constant
7. color-constant opacity-discrete shape-constant size-constant
8. color-discrete shape-discrete size-constant
9. color-discrete opacity-discrete shape-discrete
10. color-discrete opacity-discrete size-constant
11. color-discrete opacity-constant shape-discrete
12. color-discrete opacity-constant size-constant
13. color-discrete shape-constant size-constant
14. color-discrete opacity-discrete shape-constant
15. color-discrete opacity-constant shape-constant
16. color-constant shape-discrete size-constant
17. color-constant opacity-discrete shape-discrete
18. color-constant opacity-discrete size-constant
19. color-constant opacity-constant shape-discrete
20. color-constant opacity-constant size-constant
21. color-constant shape-constant size-constant
22. color-constant opacity-discrete shape-constant
23. color-discrete shape-discrete
24. color-discrete size-constant
25. color-discrete opacity-discrete
26. color-discrete opacity-constant
27. color-discrete shape-constant
28. color-constant shape-discrete
29. color-constant size-constant
30. color-constant opacity-discrete
31. color-constant opacity-constant
32. color-constant shape-constant
33. color-discrete
34. color-constant

legendContinuousSize

1. color-continuous opacity-continuous size-continuous
2. color-constant opacity-continuous size-continuous
3. color-continuous size-continuous
4. color-constant size-continuous

legendContinuousBlockSize

1. color-distribution opacity-distribution size-distribution
2. color-distribution size-distribution

legendContinuousBlock

1. color-distribution opacity-continuous
2. color-distribution

legendContinuous

1. color-continuous opacity-continuous
2. color-continuous

[hustcc]

图例组件推断关系

这个我们周一一起筛查一下，究竟哪些是需要显示图例的。比如：单测截图中的但颜色的 size 图例，就感觉默认不太合理，虽然用户通过 api 都可以调整，但是最好还是默认就相对来说是好用好看的。