add cellrank krylov optimised packages back in

[le-ander]

No description provided.

[Zethson]

Do you have an update here?

[le-ander]

No, getting this to run is rather tricky without conda. I'd day let's see if it runs at acceptable speed without these packages first yor your usecase.

[Zethson]

All right. FYI @WeilerP @AnnaChristina

[WeilerP]

Could work depending on the size of the dataset. For the tutorials using the VelocityKernel and CytoTRACEKernel, we're only using the vanilla CellRank installation, i.e., no petsc or slepc.