This change implements docker compatibile endpoint for interacting with
volumes. The code is mostly lifted from the `libpod` API handlers but
decodes and constructs data using types defined in the docker API
package.
Some notable support caveats with the current implementation:
* we don't return the nullable `Status` or `UsageData` keys when
returning volume information for inspect and create endpoints
* we don't support filters when pruning
* we return a fixed `0` for the `SpaceReclaimed` key when pruning
since we have no insight into how much space was freed from runtime
Signed-off-by: Matt Brindley <58414429+maybe-sybr@users.noreply.github.com>