fix: Incorrect corner cutting of FloatingPanel

[mhduiy]

When the background is transparent, the first time using ItemViewport to crop rounded corners, anti aliasing is already present, and the second time no longer requires anti aliasing

Issue: https://pms.uniontech.com/bug-view-271399.html

[deepin-ci-robot]

deepin pr auto review

关键摘要:

• 在FloatingPanel.qml中新增了antialiasing属性，但在dquickitemviewport_p.h中没有看到相应的属性或逻辑变化。需要确认antialiasing属性的作用和使用场景。
• 在dquickitemviewport_p.h中修改了maskTexture的创建逻辑，增加了d->antialiasing作为参数。需要验证这一改动是否符合预期效果，并确保所有使用该逻辑的地方都已经做了相应的修改。

是否建议立即修改:

• 是，需要确保新增的antialiasing属性在相关文件中被正确实现和使用，并且与现有代码库保持一致。同时，需要验证dquickitemviewport_p.h中的改动不会引入新的问题或影响现有功能。

[deepin-bot[bot]]

Doc Check bot :yellow_circle: some documents missing! File	Line	Symbol
src/private/dquickitemviewport_p.h	227	bool Dtk::Quick::DQuickItemViewportPrivate::needMaskNode

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: 18202781743, mhduiy

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