Allow changing unified property without disabling component

[mvaligursky]

Allow the GSplatComponent.unified property to be changed at runtime without requiring manual disable/enable of the component.

Changes

• Modified unified setter to automatically destroy and recreate internal data (instance/placement) when the value changes
• Simplified global-sorting example to demonstrate direct property assignment

Before

comp.enabled = false;
comp.entity.enabled = false;
comp.unified = true;
comp.enabled = true;
comp.entity.enabled = true;

After

comp.unified = true;

[willeastcott]

I'm not a fan of this naming. I prefer something like GSplatComponentSystem#getMaterial.

[mvaligursky]

yep good point, will address separately.