fix: [emblem] performance optimization

[Lighto-Ku]

replace QIcon::paint func with QPainter::drawPixmap.

Log: performance optimization

[deepin-ci-robot]

deepin pr auto review

关键摘要:

• 在代码更改中，使用了drawPixmap方法替代paint方法来绘制图标，这可能是为了优化性能。但是，这种更改是否适用于所有类型的图标，需要进行充分的测试。
• 注释中提到的“某些特殊情况下的图标”，可能需要更详细的分析或重构，以确保这种方法不会对其他图标类型造成负面影响。

是否建议立即修改:

• 是，需要确保更改后的代码不会引入新的错误或性能问题，并且与项目的其他部分兼容。同时，应该提供更多的上下文信息，以便其他开发者理解这一更改的背景和影响。

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Johnson-zs, Lighto-Ku

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