Fixed use labelShadow not setting contentSize correctly

[haiyoucuv]

Re: # Fixed use labelShadow not setting contentSize correctly

Changelog

• cocos/2d/assembler/label/text-processing.ts

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Continuous Integration

This pull request:

• needs automatic test cases check.

  Manual trigger with @cocos-robot run test cases afterward.

• does not change any runtime related code or build configuration

  If any reviewer thinks the CI checks are needed, please uncheck this option, then close and reopen the issue.

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Compatibility Check

This pull request:

• changes public API, and have ensured backward compatibility with deprecated features.
• affects platform compatibility, e.g. system version, browser version, platform sdk version, platform toolchain, language version, hardware compatibility etc.
• affects file structure of the build package or build configuration which requires user project upgrade.
• introduces breaking changes, please list all changes, affected features and the scope of violation.

[haiyoucuv]

Fixed use labelShadow not setting contentSize correctly
修复了使用labelShadow后contentSize没有设置到正确的值导致文字显示变形的问题

Before(修复前):

After(修复后):

Before with large value(修复前，使用极端值):

After with large value(修复后，使用极端值):

[github-actions]

👍 Package size ⤵ -24 bytes, old: 5195606, new: 5195582

Interface Check Report

This pull request does not change any public interfaces !

[qiuguohua]

#17886
After internal discussion, we plan to implement a button to accommodate both effects in the future. One option will proportionally scale the content while maintaining the original size, fixing the font distortion issue.The other option will automatically expand the contentSize, as described in your PR.
Currently, merging this PR might impact compatibility. Therefore, we will hold off on merging it for now.
我们内部讨论了下，我们后续会做个按钮来兼容这两种效果：
1、一种的在原有大小情况下，等比例缩放，修复字体变形的问题；
2、一种是你这个PR描述的那样，自动扩展contentSize。
目前这个PR如果合并，可能会影响兼容性。所以，暂时不合并。