Fix NodeExpandVolume

[ArielYehezkely]

• Fix NodeExpandVolume to continue to actually call lvextend when the requested capacity is larger than the current PV capacity to enable exapnsion.
• Advertise PluginCapability_VolumeExpansion_ONLINE so the external-resizer sidecar drives NodeExpandVolume per CSI spec.
• After a successful NodeExpandVolume, patch pv.Spec.CSI.VolumeAttributes[CapacityParam] with the new size via a client.MergeFrom patch so failover re-provisioning recreates the LV at the expanded size.
• Add unit tests and e2e tests for expanding PV.

[jmclong]

Thanks for adding so many tests and thanks for thinking too of the case where we need to rehydrate the expanded PV.

Can you also change controllerExpansion to true in test/external/drivers/lvm.yaml? That will enable a few more test that will do volume expansion in external e2e.

local-csi-driver/test/external/drivers/lvm.yaml

Line 26 in da4d4e8

controllerExpansion: false

[ArielYehezkely]

@jmclong The E2E tests revealed a problem that might require a wider change - the capacityParam is an immutable field which cannot be patched, this mean that re-provisioning after expansion will create the PV with the original size from creation time, I don't know if this is a blocker for the current change.
You might consider using annotations instead which are mutable but I'm leaving this to another PR.