Prefilter the invisible 3DGS before splatting on images

[Miaosheng1]

For large-scale scenes, particularly in the forward-moving street scenes, some 3D Gaussians may lie outside the current camera frustum. A better way to save memory and accelerate the speed is to filter some 3DGS that are not visible within the camera's view frustum before execute rasterization. Have you implemented this component?