feat:emphasis color inherit support

[Foreverwzh]

Brief Information

This pull request is in the type of:

• bug fixing
• new feature
• others

What does this PR do?

allow emphasis.itemStyle.color = 'inherit'

Fixed issues

• fix Set emphasis color same with normal color #11788

Details

Before: What was the problem?

The emphasis color has to be set to same value as normal color when we expect the emphasis color not change. But if we use global setting colors or default colors, this would be a big problem.

After: How is it fixed in this PR?

set emphasis.itemStyle.color = 'inherit'

Misc

• The API has been changed (apache/echarts-doc#xxx).
• This PR depends on ZRender changes (ecomfe/zrender#xxx).

Related test cases or examples to use the new APIs

test/emphasis-inherit.html

Others

Merging options

• Please squash the commits into a single one when merge.

Other information

[echarts-bot]

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[echarts-bot]

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