Volumes that are provisioned with `VolumeMode: Block` often have a
MetrucsProvider interface declared in their type. However, the
MetricsProvider should implement a GetMetrics() function. In the cases
where the storage drivers do not implement GetMetrics(), a panic can
occur.
Usual type-assertions are not sufficient in this case. All assertions
assume the interface is present. There is no straight forward way to
verify that a valid GetMetrics() function is provided.
By adding SupportsMetrics(), storage driver implementations require
careful reviewing for metrics support.
PR #97972 added support for gathering metrics for Block PVCs provided by
CSI drivers. The in-tree drivers can support at leas the most basic
metric; Capacity.
fakeVolumeHost previously implemented both the KubeletVolumeHost and
AttachDetachVolumeHost interfaces. This design makes it difficult to test the
CSIAttacher since it behaves differently depending on what type of
VolumeHost is supplied.
* Rename const for topology.../zone
* Rename const for topology.../region
* Rename const for failure-domain.../zone
* Rename const for failure-domain.../region
* Restore old names for compat
