Track PVC bound time in volume populator

[Rishita-Golla]

Description

Currently, the volume populator library lacks a metric to track the time it takes for a PVC to transition to the "bound" state. This metric would be valuable for understanding volume provisioning performance.

Proposed Solution

Introduce a new metric within the volume populator library that measures the time elapsed between the following events:
Start Time: When the volume populator begins processing a PVC request. This might not align with the PVC creation time, especially for populators using the WaitForFirstConsumer binding mode.
End Time: When the PVC reaches the "bound" state, indicating successful binding to a PersistentVolume (PV).

This metric provides insights into the efficiency of volume provisioning. Increased PVC bound times could signal underlying issues with storage provisioning or the volume populator itself. This metric is relevant across all volume populator types and is not specific to any particular storage backend.

[sunnylovestiramisu]

Note: this is a feature request of adding kube_state_metrics but NOT required for GA for lib-volume-populator.

Also "how long it takes for a pvc to be bound" is generic and not specific to lib-volume-populator. A discussion is needed for where to add such metrics.