Add a "kapp images list" command.

**Describe the problem/challenge you have**

Want an easy way of being able to list all images used by an application deployment and what top most resource they were specified in, eg., Deployment, DaemonSet, StatefulSet, or if no owner they are created from, then the Pod.

**Describe the solution you'd like**

Would like to be able to say:

```
kapp images list -a example
```

**Anything else you would like to add:**

There are already commands for:

```
kapp config-map list -a example
kapp service-account list -a example
```

This would fit in with how these are possible and have similar sort of result.

The command to list images would be useful when trying to verify the the outcome of image rewrites due to using kbld to map to hash, or when doing image relocation via imgpkg.

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