fix: jittering when dragging quick action applet

[RigoLigoRLC]

修改后拖拽时将不会实时改变overlayWindow的尺寸，避免了拖拽时产生的不流畅效果。但旧的基于全窗口模糊的效果实现将无法使用。

补充了部分关于开启模糊时拖拽事件不生效的原因的描述。

Log:

[deepin-ci-robot]

Hi @RigoLigoRLC. Thanks for your PR.

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[deepin-bot]

TAG Bot

New tag: 1.99.3
DISTRIBUTION: unstable
Suggest: synchronizing this PR through rebase #846

[deepin-bot]

TAG Bot

New tag: 1.99.4
DISTRIBUTION: unstable
Suggest: synchronizing this PR through rebase #856

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: BLumia, RigoLigoRLC

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