feat(spdk): Support changing volume size

[AaronDewes]

Which issue(s) this PR fixes:

longhorn/longhorn#8022

What this PR does / why we need it:

Currently, SPDK volumes can not be expanded. This aims at fixing this.

Special notes for your reviewer:

I've not contributed to Longhorn before and this is completely untested. I'm trying to implement & test this feature, this is just a draft.

Additional documentation or context

Depends on longhorn/longhorn-instance-manager#415

[derekbit]

Need to update the function. cliAPIVersion is always 0 for v2 volume, so skip the check.

func IsValidForExpansion(engine *longhorn.Engine, cliAPIVersion, imAPIVersion int) (bool, error) {
	if engine.Status.IsExpanding {
		return false, nil
	}
	if engine.Spec.VolumeSize == engine.Status.CurrentSize {
		return false, nil
	}
	if engine.Spec.VolumeSize < engine.Status.CurrentSize {
		return false, fmt.Errorf("the expected size %v of engine %v should not be smaller than the current size %v", engine.Spec.VolumeSize, engine.Name, engine.Status.CurrentSize)
	}

	if datastore.IsDataEngineV1(engine.Spec.DataEngine) {
		if cliAPIVersion < engineapi.CLIAPIMinVersionForExistingEngineBeforeUpgrade {
			return false, nil
		}

		if !engineapi.IsEndpointTGTBlockDev(engine.Status.Endpoint) {
			return true, nil
		}
		if cliAPIVersion < 7 {
			return false, fmt.Errorf("failed to do online expansion for the old engine %v with cli API version %v", engine.Name, cliAPIVersion)
		}
		if imAPIVersion < 3 {
			return false, fmt.Errorf("failed do online expansion for the engine %v in the instance manager with API version %v", engine.Name, imAPIVersion)
		}
	}

	return true, nil
}

[innobead]

@AaronDewes any updates?