fix Skeleton's opacity can not work normally

[bofeng-song]

Re: #
#16960
#16601

Changelog

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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.

Greptile Summary

This PR addresses issues with Skeleton opacity in the Cocos Engine, implementing changes to ensure proper opacity handling across different rendering modes.

• Modified cocos/spine/assembler/simple.ts to use a more precise EPSILON comparison for opacity calculations
• Updated cocos/spine/skeleton.ts to include node opacity in alpha value calculations for the _updateColor method
• Adjusted SkeletonCacheAnimation::render in native C++ code to incorporate entity opacity in final color calculations
• Modified SkeletonRenderer::render in native C++ code to include entity opacity in the opacity calculation

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Interface Check Report

This pull request does not change any public interfaces !

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