[Feature request] Use SHA value from `kwctl`

[nunix]

[Actual behaviour] For commands like inspect or manifest, kwctl needs the policy "name", which currently is the ://

This can bring some confusion, specially when working with the registry scheme, as it can lead someone to think that it can be used "online" (read: without pulling the image).

[Desired behaviour] Like container images, the policies also have a "hash", so it could be used for working with it locally. Example:

$ kwctl policies
+--------------------------------------------------------------+----------+---------------+----------------+----------+
| Policy                                                                                                 | Mutating  | Context aware | SHA-256            | Size          |
+--------------------------------------------------------------+----------+---------------+----------------+----------+
| registry://ghcr.io/kubewarden/policies/pod-privileged:v0.1.9      | no             | no                      | 59e34f482b40 | 21.86 kB   |
+--------------------------------------------------------------+----------+---------------+----------------+----------+

$ kwctl inspect 59e34f482b40
Details
title:              pod-privileged
description:        Limit the ability to create privileged containers
author:             Flavio Castelli
url:                https://github.com/kubewarden/pod-privileged-policy
source:             https://github.com/kubewarden/pod-privileged-policy
license:            Apache-2.0
mutating:           false
context aware:      false
execution mode:     kubewarden-wapc
protocol version:   1
...

Hope it makes sense and any other way is welcome 😄

[flavio]

Makes sense to me

[nitishm]

@flavio I took a stab at this. Please let me know if this is what you were thinking or if we want to support a --sha flag instead. In this implementation we can either pass the URI or the SHA (truncated to 12 characters) and it uses regex to figure out which is which.