fix(AxisPointer): Correct alignment for rich text tooltip labels

[geertplaisier]

Brief Information

This pull request is in the type of:

• bug fixing
• new feature
• others

What does this PR do?

Fixes the alignment for axisPointer rich labels

Fixed issues

• [Bug] axisPointer label alignment wrong when using rich text #20523

Details

Before: What was the problem?

The alignment for rich text tooltip labels are incorrect, not in the center

After: How does it behave after the fixing?

The alignment for rich text tooltip labels are now correctly centered

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

N.A.

Others

Merging options

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

Other information

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