WIP: replace Images with specific packages

[timholy]

Currently the bottleneck is gaussian_pyramid which is still in
Images.jl

[ashwani-rathee]

Can we bring pyramid functions here or somewhere more appropriate if needed?That almost empties out algorithms.jl in Images.jl if threshold ones are gone too today and much closer to a meta package than ever.

[timholy]

Pyramids should be a separate package; ImageTracking among likely many others needs them. Though perhaps they could move to ImageBase; it's a pretty fundamental concept in image processing.

[ashwani-rathee]

Should we make it a separate package then or keep it in ImageBase.jl? I am assuming it doesn't conflict with monorepo work because Images.jl is at top level and ImageBase.jl seems to be separate enough too.

[timholy]

I don't have a strong opinion, but I think since restrict is in ImageBase and we might use restrict in making fast pyramids, I think moving it to ImageBase seems fine.