add options to clean only part of the cache

[deitch]

Signed-off-by: Avi Deitcher avi@deitcher.net

- What I did

Extended lkt cache by adding some options:

• cache clean --published-only will delete all images in the cache that are available on the registry. This is a nice way of saying, "remove anything from my cache that is publicly available"
• cache rm a b c will delete specific images a, b, c
• cache rm --published-only a b c will delete specific images a, b, c but only if they are published to the registry

- How I did it

Extending the commands.

- How to verify it

CI as usual, plus ran it locally with multiple setups.

- Description for the changelog

More fine-grained control over cache cleanup.