Enhance / Test latest Ceph CSI releases 3.14 and 3.15

Looks like latest version we have tested is 3.13
https://github.com/charmed-kubernetes/ceph-csi-operator/blob/release_1.34/upstream/cephfs/version

Now, that is an upstream version that seems out of support at the moment
https://github.com/ceph/ceph-csi
 
We should test latest Ceph CSI releases 3.14 and 3.15