In order to enable the usage of CephFS shallow-copying, we must allow the user to configure the desired access modes to be used by the PVCs consumed by volsync to perform the restic copy.

CephFS 4.12 shallow-copy feature requires the use of a storageclass with `backingSnapshots: true` and for the PVCs that provision from that storage class to be ROX. Since the application PVC will likely be RWX, we need the ability for the user to configure the access modes to be used by the volsync process.