fix(legend): Fix text overflow and improve layout handling. (#20237)

[SchnWalter]

Brief Information

This pull request is in the type of:

• bug fixing
• new feature
• others

What does this PR do?

Improve the overall user experience by ensuring legends are displayed properly, avoiding overflow issues with lengthy item labels or limited space.

Additionally, a new test has been provided to demonstrate and verify the changes by comparing the behavior before and after applying the changes.

Fixed issues

• [Bug] Plain legend label overflows container if text is too long #20237: [Bug] Plain legend label overflows container if text is too long

Details

Before: What was the problem?

The legend has a width of 128px and the overflow is configured to break words, but it doesn't do anything.

After: How does it behave after the fixing?

The legend item text overflow is working correctly.

Document Info

One of the following should be checked.

• 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

• test/legend-overflow.html

Others

Merging options

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

Other information

[echarts-bot]

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[github-actions]

The changes brought by this PR can be previewed at: https://echarts.apache.org/examples/editor?version=PR-20967@ed9013d