Add PVC volume expansion

[HoustonPutman]

Resolves #709

• Implement
• Changelog
• Tests
• Documentation

[HoustonPutman]

Unfortunately, KinD does not support volume expansion by default, so we will need to find a new PVC provisioner for our integration tests.
kubernetes-sigs/kind#3734

[smoldenhauer-ish]

Suggested change

	// handleManagedCloudScaleUp does the logic of a managed and "locked" cloud scale up operation.
	// This will likely take many reconcile loops to complete, as it is moving replicas to the pods that have recently been scaled up.
	// handlePvcExpansion handles the logic of a persistent volume claim expansion operation.

[janhoy]

I just handled a volume scale for customer's customer today. Disks were full and we did the dance of updating sts, deleting it in orphan mode, adjusting each PVC manually, waiting for resize, and rolling restart of sts. A true pain :)

So is there perhaps any news on this, or is it an alternative to test this feature only on unit level or with mocks until we can use a true provisioner?