PDB & PC for Fleet

[p-se]

Rancher needs to be extended:

• add new configuration variables for Fleet PDB & PC in Rancher
• import of a new cluster should result in the Fleet cluster resource getting the spec.agentSchedulingCustomization field properly set.

Within this context, PDB and PCs must first be supported in Fleet.

[kkaempf]

@p-se what is this blocked on ?

[p-se]

@p-se what is this blocked on ?

It isn't anymore. #4162 unblocked it.