fix(datalabel): hideOverlap not work on emphasis state

[Justin-ZS]

Brief Information

This pull request is in the type of:

• bug fixing

What does this PR do?

Fix hideOverlap not working on emphasis state for data labels.

Fixed issues

• [Bug] labelOverLay.hideOverLap not work when using axisPointer triggerEmhasis #20744
  

• [Feature] Ability to hide overlap in value labels in emphasis state #19192

Details

Before: What was the problem?

When data labels have hideOverlap enabled, all overlapping labels are forcibly displayed during emphasis state (hover or other emphasis triggers), completely ignoring the overlap detection settings. This causes dense label overlapping and affects readability.

After: How does it behave after the fixing?

• Emphasis labels get the highest display priority
• Other labels that overlap with emphasis labels are intelligently hidden
• Non-overlapping labels display normally
• Original overlap handling logic is restored when exiting emphasis state

Fix Method:

1. Added EmphasisManager class to manage label overlap during emphasis state
2. Used reordering mechanism to give emphasis labels highest priority
3. Modified hideOverlap function to support pre-ordered mode, emphasis state labels also follow overlap rules
4. Added state listeners for dynamic overlap handling

Document Info

• This PR doesn't relate to document changes
• The document should be updated later
• The document changes have been made in apache/echarts-doc#xxx

Misc

ZRender Changes

• This PR depends on ZRender changes (ecomfe/zrender#xxx).

Related test cases or examples to use the new APIs

N.A.

Others

Merging options

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

Other information

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[github-actions]

The changes brought by this PR can be previewed at: https://echarts.apache.org/examples/editor?version=PR-21233@88eb99f

[Justin-ZS]

@100pah Could you help to review the PR? Thanks!

[Justin-ZS]

@plainheart @pissang Could you help to review the PR? Thanks!

[Ovilia]

@Justin-ZS Hi, I've voted you to be a committer of Apache ECharts due to your continuous contribution. Can you provide an Email address for me to send our invitation. Please add my We-chat oviliazhang with a note "Justin-ZS" so that I can add you to our committer group. Thanks!

[Justin-ZS]

@Justin-ZS Hi, I've voted you to be a committer of Apache ECharts due to your continuous contribution. Can you provide an Email address for me to send our invitation. Please add my We-chat oviliazhang with a note "Justin-ZS" so that I can add you to our committer group. Thanks!

Thank you! I’m so happy to hear that!
I've sent the We-chat friend request. My Email is [email protected]