[BUG]: Performance dropping when moving multiple nodes

[l3enQ]

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2. Click on '....'
3. Scroll down to '....'
4. See error

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[HamedMasafi]

I checked and saw that in the mouse movement event, the position relative to the last point is saved, which can cause lag. I changed this routine to coordinates relative to the click point.

https://github.com/Roniasoft/NodeLink/blob/wip/movement_speed/resources/View/ObjectSelectionView.qml#L106

https://github.com/Roniasoft/NodeLink/blob/wip/movement_speed/resources/View/ObjectSelectionView.qml#L130

Also, I added a flag in the bottom line so that PortView.qml::opacity properties do not change when the Nodes are moving.

https://github.com/Roniasoft/NodeLink/blob/wip/movement_speed/resources/View/PortView.qml#L39

My changes are available on the movement_speed branch. I would be grateful if someone could test them.

[HamedMasafi]

Memory managment checked; There's no memory leak. Nodes destroy correctly after deleting from scene but I found that some function in I_Scene.qml can be written in better way. I'll send a PR