Update `CModelRenderer` to expose its `m_modelChangeEvent`

[adriengivry]

Problem this feature should fix

Currently the CModelRenderer manually call various components methods, such as:

• CMaterialRenderer::UpdateMaterialList()
• CSkinnedMeshRenderer::NotifyModelChange()

This design defeats the points of having this event in the first place.

Expected solution

We should make this event public, and let other components subscribe to it.