Refactor PatchSet to be contained in a separate package for reusability.

cluster-autoscaler/simulator/common/patch.go

cluster-autoscaler/simulator/common/patch_test.go

cluster-autoscaler/simulator/common/patchset.go

cluster-autoscaler/simulator/common/patchset_test.go

...utoscaler/simulator/dynamicresources/snapshot/snapshot.go

...oscaler/simulator/dynamicresources/snapshot/test_utils.go