Proposal: Remove IndependentMOKernel and IntrinsicCoregionMOKernel

[devmotion]

Copied from Slack:

BTW I propose to remove the IndependentMOKernel ane the IntrinsicCoregionMOKernel since they are just KernelTensorProducts with a WhiteKernel and a yet to define MatrixKernel (maybe a bad name but generally useful IMO). Of course, we can still keep a function that constructs them in a convenient way, as we do for other single-output kernels. And one could also specialize kernelmatrix for them if needed.

[david-vicente]

Copied from Slack:

[Offtopic] Is this Julia's Slack, or a private one?

[willtebbutt]

@devmotion on second thought, I agree regarding the ICM, but I think our IndependentMOKernel is probably just not what we really want it to be -- I think it should probably comprise a vector of kernels, rather than a single kernel being used for all dimensions (I'm not sure how this one slipped through to be honest).