use ResourceList for capacity

[pawanpraka1]

Describe the problem/challenge you have

Currently capacity is string. We should move towards ResourceList to store the capacity.

[dsharma-dc]

Unsure of reasons behind needing this. Checking if it's not something that will have side-effects or breaking behaviour.

[dsharma-dc]

This pertains to changing the type of Capacity in VolumeInfo.

// VolumeInfo defines LVM info
type VolumeInfo struct {

[...]

	// Capacity of the volume
	// +kubebuilder:validation:Required
	// +kubebuilder:validation:MinLength=1
	Capacity string `json:"capacity"`

[avishnu]

This needs to be consistent across all engines. Need to assess the impact of this modification.